Blood & Lymphoreticular

Chronic myeloid leukemia: TKI therapy

Clinical Overview and When to Suspect CML

— Median age at diagnosis ~65; slight male predominance; ~15% of adult leukemias in the US

— Only confirmed environmental risk: prior ionizing radiation exposure

— Chronic phase (CP): <10% blasts in blood/marrow; >90% present here in the TKI era

— Accelerated phase (AP): 10–19% blasts, basophils ≥20%, persistent thrombocytopenia or rising platelets, clonal evolution

— Blast phase (BP): ≥20% blasts (myeloid 2/3, lymphoid 1/3) — behaves like acute leukemia

— Incidental leukocytosis (often >50–100k) on routine CBC with left-shifted myeloid series (myelocytes, metamyelocytes, segs, basophilia, eosinophilia) and no infection

— Splenomegaly causing LUQ fullness, early satiety, or weight loss

— Constitutional symptoms: fatigue, night sweats, low-grade fever

— Hyperviscosity/leukostasis (priapism, visual changes, dyspnea) when WBC very high

— Gout or renal stones from high cell turnover

— CML lacks toxic granulation/Döhle bodies; has low leukocyte alkaline phosphatase (LAP) score (largely historical)

— Basophilia is a near-universal red flag for a myeloproliferative process

— TKI therapy has converted CML into a chronic, ambulatory-managed malignancy with near-normal life expectancy when monitored correctly

— Most exam vignettes test monitoring milestones, resistance, and TKI-specific toxicities rather than initial diagnosis.

Chronic myeloid leukemia (CML) is a myeloproliferative neoplasm defined by the t(9;22)(q34;q11) Philadelphia chromosome producing the BCR-ABL1 fusion with constitutive tyrosine kinase activity driving unregulated myeloid proliferation.

Epidemiology

Three phases — clinically and prognostically distinct

When to suspect on Step 3

Differential clues vs. reactive leukocytosis

Board pearl: Any otherwise-well adult with WBC >50,000, basophilia, splenomegaly, and no infectious source is CML until BCR-ABL1 testing proves otherwise — order peripheral blood BCR-ABL1 by qPCR before any bone marrow procedure to expedite triage.

Why this matters for Step 3

Presentation Patterns and Key History

— Asymptomatic incidental finding (~40–50%): routine CBC for an unrelated visit (preop, insurance physical, annual exam) shows striking leukocytosis with myeloid left shift

— Constitutional/hyperproliferative: weeks-to-months of fatigue, night sweats, low-grade fever, weight loss, early satiety, LUQ discomfort or referred left shoulder pain from splenomegaly

— Hyperleukocytosis/leukostasis: priapism, tinnitus, blurred vision, headache, dyspnea, confusion — typically WBC >100–200k

— Duration of symptoms — indolent course over months favors CP; rapid worsening, bone pain, bleeding, or extramedullary masses raise concern for AP/BP

— Bleeding or thrombosis despite elevated platelets (qualitative platelet dysfunction is common)

— Prior radiation exposure (atomic, therapeutic, occupational) — only validated risk factor

— Cardiovascular history: CAD, PAD, prior stroke, hypertension, diabetes, smoking, dyslipidemia — directly drives TKI selection (nilotinib and ponatinib are vasculopathic)

— Pulmonary history: COPD, prior effusion, CHF — relevant for dasatinib (pleural effusions, pulmonary HTN)

— Hepatitis B status: TKIs can cause HBV reactivation

— QT-prolonging meds, electrolyte issues: nilotinib prolongs QT

— Reproductive plans: TKIs are teratogenic

— Gout/joint pain (hyperuricemia from turnover)

— Easy bruising, gum bleeding, epistaxis

— Visual changes, priapism (leukostasis red flags)

— CML is not familial — reassure patients; no genetic screening of relatives

— Document fertility goals — relevant for treatment-free remission counseling

Three classic presentation archetypes

Key history elements to elicit

Review of systems prompts

Key distinction: CML symptoms develop gradually over months; abrupt onset of fever, bone pain, lymphadenopathy, or cytopenias suggests blast crisis or de novo acute leukemia, not new chronic-phase CML.

Family and social history

Step 3 management: At the index outpatient visit, simultaneously order CBC with differential, peripheral smear, CMP, LDH, uric acid, BCR-ABL1 qPCR (IS), hepatitis B serologies, HIV, pregnancy test, ECG with QTc, lipid panel, HbA1c, and refer to hematology — this single-visit bundle accelerates time to TKI initiation.

Physical Exam Findings (and Hemodynamic Assessment)

— Most CP-CML patients appear well; tachycardia or weight loss suggest higher disease burden

— Fever without source raises suspicion for AP/BP transformation or concurrent infection (especially if neutrophils functionally impaired)

— Splenomegaly in 40–70% at diagnosis; can extend to the pelvis

— Measure spleen size below the left costal margin in cm in the midclavicular line at every visit — it's a clinical response marker

— Hepatomegaly less common; massive hepatosplenomegaly suggests advanced phase

— Palpable spleen rub or LUQ tenderness may indicate splenic infarction (more common with extreme leukocytosis)

— Petechiae, ecchymoses, mucosal bleeding suggest qualitative platelet dysfunction or thrombocytopenia (concerning in AP/BP)

— Pallor from anemia

— Sweet syndrome (neutrophilic dermatosis) — paraneoplastic association

— Leukemia cutis (violaceous nodules) — suggests blast phase

— CP-CML typically lacks lymphadenopathy — its presence should prompt evaluation for lymphoid blast crisis or alternative diagnosis (CLL, lymphoma)

— Document baseline BP, peripheral pulses, ABI if PAD risk, JVP, lung auscultation

— Baseline weight and edema assessment — dasatinib causes fluid retention/pleural effusions

— Cranial nerve deficits, papilledema, or focal findings → CNS leukostasis or CNS blast involvement

— Priapism in males is a urologic emergency and leukostasis sign

— Hypoxia, tachypnea, altered mental status with WBC >100k → leukostasis emergency

— Treat with hydration, allopurinol/rasburicase, urgent hydroxyurea ± leukapheresis while awaiting BCR-ABL1 confirmation

Vital signs and general appearance

Abdominal exam — the highest-yield finding

Skin and mucosa

Lymph node exam

Cardiopulmonary baseline (critical for TKI selection)

Neurologic

Hemodynamic assessment in hyperleukocytosis

CCS pearl: On a CCS case opening with WBC 250k and confusion, don't wait for BCR-ABL1 — order IV fluids, allopurinol, hydroxyurea 50 mg/kg/day, type and screen, and consult hematology immediately; advance the clock and recheck WBC, electrolytes, uric acid, and mental status.

Diagnostic Workup — Initial Labs, Smear, and Baseline Studies

— Leukocytosis typically 50,000–300,000/µL; left-shifted myeloid series with all stages of maturation visible (myeloblasts, promyelocytes, myelocytes, metamyelocytes, bands, segs)

— Basophilia (almost universal) and eosinophilia

— Thrombocytosis in ~30–50%; thrombocytopenia raises concern for AP/BP

— Mild normocytic anemia common

— Full spectrum of granulocyte maturation, basophilia, myelocyte bulge (myelocytes > metamyelocytes), few circulating blasts in CP (<2%)

— Pseudo-Pelger-Huët cells or dysplasia suggest advanced phase

— LDH, uric acid elevated from high turnover

— Vitamin B12 elevated (transcobalamin from neutrophils) — classic boards factoid

— LFTs, creatinine — baseline for TKI dosing

— Electrolytes including Mg, K, Ca, phosphate — replete before nilotinib (QT)

— Peripheral blood BCR-ABL1 by qRT-PCR on the International Scale (IS) — both diagnostic and the gold standard for ongoing monitoring

— Detects p210 transcript in classic CML (e13a2/e14a2); p190 in some CML and Ph+ ALL; p230 in rare neutrophilic CML

— FISH for BCR-ABL1 is acceptable if PCR unavailable but less sensitive for monitoring

— ECG with QTc (especially before nilotinib)

— HBV surface antigen, core antibody, surface antibody — reactivation risk

— Lipid panel, fasting glucose/HbA1c — nilotinib raises both

— Pregnancy test in reproductive-age women

— Lipase/amylase baseline (nilotinib pancreatitis)

— Historically low in CML, high in leukemoid reaction — largely supplanted by BCR-ABL1 PCR

Complete blood count with differential

Peripheral blood smear — recognizable pattern

Chemistry and turnover markers

Confirmatory molecular testing (essential)

Pre-TKI baseline workup (Step 3 favorite)

Leukocyte alkaline phosphatase (LAP) score

Board pearl: Elevated B12, low LAP score, basophilia, and a myelocyte bulge on smear in an adult with WBC >50k is the classic Step 3 quartet pointing to CML before BCR-ABL1 results return.

Diagnostic Workup — Confirmatory Studies and Staging

— Establishes phase (CP vs. AP vs. BP) by quantifying blasts and basophils

— Hypercellular marrow (often 100%) with myeloid hyperplasia, left shift, increased megakaryocytes (often small/dwarf), and reticulin fibrosis

— Sea-blue histiocytes and pseudo-Gaucher cells from increased turnover

— Conventional karyotype on ≥20 metaphases confirms t(9;22) and detects additional chromosomal abnormalities (ACAs) in Ph+ cells — markers of clonal evolution and AP-defining if high-risk (e.g., +8, +Ph, i(17q), +19, complex karyotype)

— FISH supplements when karyotype fails

— Quantitative BCR-ABL1 (IS) baseline transcript level for future log-reduction tracking

— ABL1 kinase domain mutation analysis — not routinely at diagnosis; reserved for treatment failure or progression

— CP: <10% blasts in blood/marrow, no AP/BP criteria

— AP: 10–19% blasts, peripheral basophils ≥20%, platelets <100k unrelated to therapy or >1000k unresponsive to therapy, additional clonal abnormalities in Ph+ cells, increasing spleen/WBC unresponsive to therapy

— BP: ≥20% blasts in blood/marrow, extramedullary blast proliferation, or large blast foci on biopsy

— ELTS score (EUTOS Long-Term Survival) preferred in TKI era — uses age, spleen size, platelets, blast %; stratifies low/intermediate/high risk and predicts CML-specific mortality

— Sokal and Hasford are older; ELTS is current Step 3-preferred

— Abdominal exam usually suffices; ultrasound or CT only if exam ambiguous or splenic infarct suspected

— No routine PET or CNS imaging unless BP or symptoms

Bone marrow biopsy and aspirate — required at diagnosis

Cytogenetics on marrow

Molecular baseline

Phase definition (WHO/ELN 2022 essentials)

Risk score calculation at diagnosis

Imaging

Step 3 management: Order at the single staging visit — bone marrow aspirate/biopsy with karyotype, FISH for BCR-ABL1, flow cytometry (if blasts), and quantitative BCR-ABL1 IS — then calculate ELTS and document phase before selecting a TKI.

Risk Stratification and First-Line Management Logic

— Achieve deep, durable molecular response to prevent progression to AP/BP

— Restore normal life expectancy (now approaches age-matched controls in CP-CML responders)

— In selected patients, achieve treatment-free remission (TFR) after sustained deep molecular response

— Chronic phase: start a TKI; vast majority managed entirely outpatient

— Accelerated phase: TKI (often a 2G-TKI) ± consideration of allogeneic HCT in selected patients

— Blast phase: TKI + acute leukemia–type induction chemotherapy (myeloid or lymphoid backbone) → allogeneic HCT in responders

— Low-risk ELTS: imatinib is reasonable (cost, tolerability, decades of safety) or a 2G-TKI if TFR is a goal

— Intermediate/high-risk ELTS: favor a second-generation TKI (dasatinib, nilotinib, or bosutinib) for faster, deeper responses and lower progression risk

— Patient comorbidities drive selection as much as risk score

— Cardiovascular disease, PAD, diabetes, hyperlipidemia: avoid nilotinib and ponatinib; favor imatinib or bosutinib

— Pulmonary disease, pleural effusion history, pulmonary HTN, on anticoagulation: avoid dasatinib

— GI/IBD history: bosutinib causes diarrhea — caution

— Pancreatitis history: caution with nilotinib

— QT prolongation/electrolyte issues: avoid nilotinib

— Hydroxyurea to lower WBC while awaiting BCR-ABL1 confirmation and TKI start

— Allopurinol and hydration for tumor lysis prophylaxis

Goals of therapy in the TKI era

Phase-driven framework

Risk-stratified first-line TKI selection in CP

Comorbidity-matched TKI choices

Pretreatment cytoreduction

Board pearl: A 58-year-old with prior MI and diabetes newly diagnosed with CP-CML — choose imatinib or bosutinib, never nilotinib or ponatinib first-line, because of vascular-occlusive risk.

Step 3 management: Document phase, ELTS, comorbidities, HBV status, ECG/QTc, lipids, glucose, and reproductive plans before selecting a TKI — this is the perfect ambulatory-management vignette.

Pharmacotherapy — TKI Regimens in Depth

— Dose: 400 mg PO daily (CP); 600–800 mg in AP/BP

— Take with food and a large glass of water

— Toxicities: edema (periorbital), muscle cramps, GI upset, rash, cytopenias, transaminitis, hypophosphatemia

— Generic, low cost — often preferred first-line in low-risk, comorbid, or cost-constrained patients

— Dose: 100 mg daily (CP); 140 mg in AP/BP

— Most potent CNS penetration — used when CNS blast disease present

— Toxicities: pleural effusion, pulmonary arterial hypertension, thrombocytopenia, bleeding (platelet inhibition), QT prolongation

— Avoid in COPD, CHF, on anticoagulation

— Dose: 300 mg BID first-line (400 mg BID second-line); fasting — no food 2 h before, 1 h after

— Toxicities: QT prolongation, sudden cardiac death (boxed warning), peripheral arterial occlusive disease, hyperglycemia, hyperlipidemia, pancreatitis, hyperbilirubinemia (Gilbert-like)

— Avoid: CAD, PAD, prior stroke, uncontrolled DM/lipids, long QT, electrolyte derangement

— Dose: 400 mg daily first-line

— Toxicity hallmark: diarrhea (early, usually self-limited), transaminitis, rash

— Favorable cardiovascular profile — useful in vasculopathic patients

— Dose: 45 mg daily, often de-escalated to 15 mg upon response (OPTIC strategy)

— Only TKI active against T315I mutation

— Boxed warning: arterial and venous thromboembolism, MI, stroke, hepatotoxicity, heart failure

— Reserved for T315I or multi-TKI failure

— Allosteric ABL myristoyl pocket binder

— Approved for CP-CML after ≥2 prior TKIs and for T315I; favorable toxicity profile (less cardiovascular signal)

— All TKIs are CYP3A4 substrates — avoid strong inducers (rifampin, phenytoin, carbamazepine, St. John's wort) and inhibitors (azoles, macrolides, grapefruit)

— PPIs/H2 blockers reduce dasatinib and bosutinib absorption — separate dosing or avoid

Imatinib (1st-generation)

Dasatinib (2G)

Nilotinib (2G)

Bosutinib (2G)

Ponatinib (3G)

Asciminib (STAMP inhibitor)

Drug interactions

Board pearl: A CP-CML patient on dasatinib develops dyspnea and a unilateral pleural effusion — hold dasatinib, diurese, consider steroids, and switch TKI; this is the classic dasatinib pleural effusion vignette.

Molecular Monitoring and Response-Adapted Management

— Every 3 months until major molecular response (MMR) is achieved and confirmed

— Then every 3–6 months indefinitely

— CBC every 2 weeks until count recovery, then monthly, then every 3 months

— 3 months: BCR-ABL1 IS ≤10% (optimal); >10% = warning, repeat in 1–3 months

— 6 months: ≤1%

— 12 months: ≤0.1% (MMR / MR3)

— Sustained MR4 (≤0.01%) and MR4.5 (≤0.0032%) are deeper responses required for TFR consideration

— BCR-ABL1 IS >10% at 6 months confirmed, or >1% at 12 months, or loss of previously achieved MMR (confirmed), or development of AP/BP, or new ACAs in Ph+ cells

— Confirm adherence (most common reason for rising transcripts)

— Check drug interactions and absorption (PPIs, fasting state)

— Send ABL1 kinase domain mutation analysis

– T315I → ponatinib or asciminib (others are inactive)

– F317L, V299L → avoid dasatinib

– Y253H, E255K/V, F359V/C → avoid nilotinib

— Switch to alternative TKI matched to mutation and comorbidities

— CP-CML on TKI ≥5 years, sustained MR4 or deeper for ≥2 years, no prior AP/BP, typical e13a2/e14a2 transcript, access to monthly PCR monitoring for 6 months, then every 2–3 months

— ~50% relapse; nearly all regain response on TKI resumption

— Not routine if PCR is responding; obtain for suspected progression, loss of response, or atypical transcript not trackable by PCR

Quantitative BCR-ABL1 (IS) is the workhorse — checked on peripheral blood

Standard monitoring cadence in CP-CML on TKI

ELN 2020 milestones — the Step 3 sweet spot

Definition of treatment failure (triggers TKI switch)

Action at failure or warning

Treatment-free remission (TFR) criteria — Step 3 ambulatory pearl

Repeat bone marrow

CCS pearl: When a CCS patient on imatinib has rising BCR-ABL1 at 12 months, order ABL1 kinase domain mutation testing and confirm adherence before switching TKI — switching blindly is a high-yield wrong answer.

Special Populations — Elderly and Renal/Hepatic Impairment

— CML is a disease of older adults; age alone is not a contraindication to TKI therapy

— Life expectancy on effective TKI approaches age-matched peers

— Favor imatinib or bosutinib in older patients with cardiovascular risk; avoid nilotinib/ponatinib if vascular disease

— Greater sensitivity to edema, cytopenias, fatigue, and drug interactions (polypharmacy)

— Watch for falls from cramps/myalgias on imatinib

— Imatinib: reduce dose if CrCl <60; avoid if CrCl <20 unless necessary; renally cleared metabolites

— Dasatinib: primarily hepatic — minimal renal adjustment

— Nilotinib: minimal renal clearance; caution with electrolytes (Mg, K) that affect QT

— Bosutinib: reduce to 300 mg if CrCl 30–50; 200 mg if <30

— Ponatinib: no specific renal adjustment; monitor for fluid retention and hypertension

— All TKIs are hepatically metabolized — baseline LFTs, then monthly, then every 3 months

— Dose reductions per labeling for moderate-to-severe hepatic impairment

— Bosutinib has higher transaminitis rates; nilotinib raises bilirubin (UGT1A1 inhibition — Gilbert-like)

— Hold TKI for grade ≥3 transaminitis (>5× ULN) or hyperbilirubinemia and resume at reduced dose

— Greater risk of AKI — hydrate, allopurinol; rasburicase if uric acid very high or G6PD-negative

— PPIs with dasatinib/bosutinib reduce absorption — switch to famotidine spaced 10 h apart or stop

— Warfarin + TKIs — monitor INR closely

— Statins — nilotinib raises lipids; check interactions

— QT-prolonging meds with nilotinib (ondansetron, fluoroquinolones, methadone)

Elderly patients (>65, often >75)

Renal impairment

Hepatic impairment

Tumor lysis precautions in elderly

Polypharmacy review (Step 3 favorite)

Step 3 management: In a 78-year-old on furosemide, omeprazole, warfarin, and atorvastatin with new CP-CML, choose imatinib, switch PPI to famotidine if dasatinib were needed, replete K/Mg, and book INR check 1 week after TKI start.

Board pearl: Hepatic dose reduction is required for every TKI — never forget baseline and serial LFTs.

Special Populations — Pregnancy, Fertility, and Pediatrics

— All TKIs are teratogenic (especially first trimester); imatinib associated with skeletal, renal, and CNS malformations

— Effective contraception is mandatory for both women and men of reproductive potential while on TKI

— Pregnancy test before initiation and periodically

— Achieve stable deep molecular response (MR4 or deeper) for ≥2 years before considering pregnancy

— Discontinue TKI before conception with monthly PCR monitoring

— If molecular relapse during pregnancy:

– Interferon-alfa is the preferred cytoreductive agent (not teratogenic, does not cross placenta)

– Leukapheresis for very high counts

– Avoid hydroxyurea (especially 1st trimester) and TKIs throughout pregnancy if possible

— Resume TKI postpartum; breastfeeding is contraindicated on TKI (drug excreted in milk)

— Stop TKI immediately; multidisciplinary counseling with hematology, MFM, and the patient regarding risks

— First-trimester exposure carries highest teratogenicity risk but does not mandate termination

— TKIs have not been clearly associated with birth defects when the father is on therapy at conception, but sperm banking before initiation is reasonable for younger men

— Rare (<5% of pediatric leukemias); usually CP at diagnosis

— Imatinib, dasatinib, and nilotinib are FDA-approved in pediatrics

— Growth retardation (especially imatinib in prepubertal children) is a unique pediatric AE — monitor height velocity

— Consider allogeneic HCT earlier in pediatric AP/BP given longer life expectancy

— Higher disease aggressiveness, lower TKI response rates

— Fertility counseling and TFR planning are central to longitudinal care

Pregnancy and TKIs

Planning pregnancy in a woman with CML

Unplanned pregnancy on TKI

Male fertility

Pediatric CML

Adolescents and young adults

Key distinction: A young woman with CML wanting future pregnancy must achieve sustained MR4 for ≥2 years on TKI before attempting conception — anything less risks rapid molecular relapse without a safe in-pregnancy substitute.

Step 3 management: Pregnant patient with newly diagnosed CP-CML and WBC 180k — start interferon-alfa, hydrate, allopurinol, and defer TKI until postpartum; consult MFM and hematology.

Complications and Adverse Outcomes

— Accelerated phase → blast phase is the dreaded trajectory; far less common in the TKI era but still occurs with nonadherence, resistance, or high-risk biology

— Blast phase: ~2/3 myeloid, 1/3 lymphoid; median survival historically <1 year — improved with TKI + chemo + HCT

— Pulmonary, CNS, and ocular microvascular sludging

— Priapism in males — urologic emergency

— Treat with hydroxyurea, hydration, allopurinol/rasburicase, and leukapheresis for symptomatic cases

— Hyperuricemia, hyperkalemia, hyperphosphatemia, hypocalcemia, AKI

— Prophylax with allopurinol; use rasburicase for high uric acid

— Massive splenomegaly + sudden LUQ pain → imaging; usually managed supportively

— Imatinib: fluid retention/periorbital edema, cramps, hypophosphatemia, cytopenias

— Dasatinib: pleural effusion (often unilateral, recurrent), pulmonary arterial hypertension (rare, reversible on discontinuation), bleeding from platelet inhibition

— Nilotinib: arterial occlusive events (MI, stroke, PAD), QT prolongation, hyperglycemia, hyperlipidemia, pancreatitis

— Ponatinib: dose-dependent arterial thrombosis, heart failure, hepatotoxicity, pancreatitis

— Bosutinib: diarrhea (usually weeks 1–4), transaminitis

— Nilotinib and ponatinib accelerate atherosclerosis — annual lipid, glucose, BP optimization is secondary prevention for CML patients

— Cytopenias most common in first 3 months — dose-hold for ANC <1.0 or platelets <50k, resume at reduced dose after recovery

— Screen at baseline; prophylactic entecavir or tenofovir for HBsAg+ and consider for HBcAb+ patients on TKI

— Chronic fatigue, GI symptoms, financial toxicity, adherence fatigue — structured patient-reported outcome assessment at follow-ups

Disease progression

Hyperleukocytosis and leukostasis

Tumor lysis syndrome

Splenic infarction or rupture

TKI-specific complications

Cardiometabolic late effects

Hematologic toxicity

Hepatitis B reactivation

Quality-of-life burden

Board pearl: New unilateral pleural effusion in a CML patient = dasatinib until proven otherwise — hold, evaluate, treat with diuretics ± steroids, and switch TKI if recurrent or severe.

When to Escalate — ICU, Consult, and Inpatient Triage

— Stable CP-CML on TKI is an ambulatory disease with hematology clinic follow-up every 1–3 months initially

— Primary care manages cardiovascular risk, vaccinations, and routine screening in parallel

— New leukocytosis with basophilia, splenomegaly, or myelocyte bulge

— Positive BCR-ABL1 on peripheral blood

— Treatment failure milestones missed

— Rising BCR-ABL1 transcripts confirmed on repeat

— Symptomatic leukostasis (visual changes, dyspnea, confusion, priapism)

— WBC >100k with end-organ dysfunction

— Tumor lysis syndrome with AKI or electrolyte emergencies

— Blast crisis (≥20% blasts) — manage as acute leukemia

— Severe TKI toxicity: grade 4 cytopenias with bleeding/infection, severe pleural effusion requiring drainage, acute pancreatitis, hepatotoxicity

— Splenic rupture or infarction with hemodynamic compromise

— Hemodynamic instability, respiratory failure from leukostasis or massive effusion

— DIC complicating blast crisis (especially lymphoid)

— Acute MI/stroke from ponatinib/nilotinib

— Hematology/oncology: all cases

— Cardiology: baseline if vasculopathic TKI considered; emergent for ischemic events

— Pulmonology: persistent pleural effusion or suspected pulmonary HTN on dasatinib

— MFM/Obstetrics: pregnant patients

— Urology: priapism

— Stem cell transplant team: AP, BP, T315I refractory disease, multi-TKI failure

— Failure of multiple TKIs including ponatinib/asciminib in eligible patients

— Accelerated phase not achieving deep response

— Blast phase after induction

Outpatient (most CP-CML)

Indications for hematology referral (same day or urgent)

Indications for inpatient admission

Indications for ICU

Subspecialty consults

Allogeneic HCT indications (Step 3 awareness)

CCS pearl: Patient with WBC 320k, confusion, hypoxia → admit to ICU, IV fluids, allopurinol, hydroxyurea, oxygen, consult heme for leukapheresis, type and screen, ECG, lipase, HBV serologies, BCR-ABL1, and advance the clock to reassess WBC and mental status every few hours.

Key Differentials — Other Myeloproliferative and Leukemoid Causes

— WBC often >50k from severe infection, severe inflammation, or solid tumors (especially with G-CSF)

— Smear shows toxic granulation, Döhle bodies, vacuoles in neutrophils

— High LAP score, negative BCR-ABL1, no basophilia, no splenomegaly typically

— Resolves with treatment of underlying cause

— JAK2 V617F (~95%); predominant erythrocytosis with secondary thrombocytosis/leukocytosis

— Low erythropoietin, splenomegaly, pruritus, erythromelalgia

— Negative BCR-ABL1

— Sustained thrombocytosis >450k; JAK2, CALR, or MPL mutations

— Mild leukocytosis without left shift; no basophilia

— Negative BCR-ABL1 — required to exclude CML before diagnosing ET

— Teardrop cells (dacrocytes), leukoerythroblastosis, marrow fibrosis, massive splenomegaly

— JAK2/CALR/MPL mutations; BCR-ABL1 negative

— Mature neutrophilia without significant left shift; CSF3R T618I mutation

— No basophilia; BCR-ABL1 negative

— Persistent monocytosis ≥1.0×10⁹/L (and ≥10%) with dysplasia

— BCR-ABL1 negative; overlap MDS/MPN

— Neutrophilia with dysgranulopoiesis, no Philadelphia chromosome; SETBP1, ETNK1 mutations

Leukemoid reaction (reactive leukocytosis)

Polycythemia vera (PV)

Essential thrombocythemia (ET)

Primary myelofibrosis (PMF)

Chronic neutrophilic leukemia (CNL)

Chronic myelomonocytic leukemia (CMML)

Atypical CML, BCR-ABL1 negative

Step 3 management: Any adult with chronic unexplained myeloid leukocytosis gets BCR-ABL1 testing first — a negative result then triggers JAK2/CALR/MPL and CSF3R workups to classify the MPN.

Board pearl: Basophilia + myelocyte bulge + low LAP = CML; toxic granulation + Döhle bodies + high LAP = leukemoid reaction. This single contrast resolves the most common boards differential.

Key Differentials — Other-Category Mimics

— ≥20% blasts in blood or marrow; rapid onset of cytopenias, bleeding, infections

— Auer rods on smear; flow cytometry confirms myeloid lineage

— Can arise as CML blast crisis — BCR-ABL1 distinguishes de novo AML from BP-CML; treatment differs (TKI added in Ph+)

— Adults: Ph+ ALL has BCR-ABL1, usually p190 transcript (vs. p210 in CML)

— Distinguished by lymphoblast morphology, lineage markers (TdT+, CD19+, CD10+), absence of chronic-phase history

— Mature lymphocytosis with smudge cells; CD5+/CD23+/CD19+ flow

— Older adults — easily confused on cursory CBC reading if only "leukocytosis" is noted

— Reactive atypical lymphocytosis, not myeloid; pharyngitis, lymphadenopathy, splenomegaly

— Monospot/EBV serologies

— Glucocorticoids, lithium, G-CSF, epinephrine — neutrophilia without immature forms or basophilia

— Persistent eosinophilia >1.5k with organ damage

— FIP1L1-PDGFRA fusion — TKI-responsive (imatinib) but not BCR-ABL1

— Differential for "another TKI-responsive myeloid neoplasm"

— KIT D816V; tryptase elevation; skin involvement

— Can have basophilia/eosinophilia mimicking MPN

— Leukemoid reaction with appropriate clinical context

— Especially non-small cell lung, GI, GU — G-CSF–producing tumors

Acute myeloid leukemia (AML)

Acute lymphoblastic leukemia (ALL)

CLL/small lymphocytic lymphoma

Infectious mononucleosis / viral lymphocytosis

Pertussis (in children) — marked lymphocytosis

Drug-induced leukocytosis

Hypereosinophilic syndromes

Systemic mastocytosis

Severe infection (TB, endocarditis, abscess)

Solid tumor with paraneoplastic leukocytosis

Key distinction: BCR-ABL1 positivity is the single defining test that distinguishes CML from every other myeloproliferative or reactive cause of leukocytosis — order it early and don't rely on smear morphology alone.

Board pearl: A vignette with myeloid leukocytosis plus eosinophilia and a TKI-responsive mass effect but negative BCR-ABL1 should make you think FIP1L1-PDGFRA hypereosinophilic syndrome — also imatinib-responsive.

Long-Term Plan, Adherence, and Treatment-Free Remission

— Most patients remain on TKI indefinitely; only a minority qualify for TFR attempts

— Adherence is the single strongest determinant of outcome — <90% adherence dramatically lowers MMR rates and raises progression risk

— Once-daily dosing when possible (imatinib, dasatinib, bosutinib) vs. BID (nilotinib)

— Pillboxes, smartphone reminders, mail-order pharmacy

— Address financial toxicity — manufacturer assistance, generic imatinib, 340B programs

— Address GI side effects (antiemetics, loperamide for bosutinib diarrhea) early to prevent self-discontinuation

— Aggressive control of BP, LDL, glucose, smoking cessation for all patients on TKI, especially nilotinib/ponatinib

— Statin therapy per ASCVD risk; aspirin per standard primary/secondary prevention guidelines

— Annual lipid panel, HbA1c, ECG/QTc on nilotinib

— Annual influenza, COVID-19 boosters, pneumococcal (PCV20 or PCV15+PPSV23), recombinant zoster (Shingrix)

— Avoid live vaccines in active disease or cytopenias

— Maintain age-appropriate screening (colon, breast, cervical, lung); CML patients have slightly elevated risk of second malignancies on long-term TKI

— Eligibility: CP-CML, TKI ≥5 years, sustained MR4 for ≥2 years, typical e13a2/e14a2 transcript, willing/able to do monthly PCR for 6 months, then every 2 months for 6 months, then every 3 months indefinitely

— ~50% relapse within 24 months, usually within first 6 months

— Re-initiate TKI promptly upon loss of MMR; near-universal regaining of response

— TKI withdrawal syndrome (musculoskeletal pain) in ~30% — usually self-limited, NSAIDs or short-course steroids

Ongoing TKI is the foundation

Adherence strategies (Step 3 ambulatory medicine)

Cardiovascular secondary prevention

Vaccinations

Cancer screening

Treatment-free remission attempt

Step 3 management: Patient on imatinib 7 years with stable MR4.5 for 3 years asks about stopping — confirm eligibility, switch labs to monthly PCR, document adherence to monitoring plan, then trial discontinuation with hematology co-management.

Board pearl: TFR is not "cure" — patients remain on lifelong PCR surveillance even after successful discontinuation.

Follow-Up, Monitoring, and Counseling Cadence

— Weeks 1–2: clinic visit, CBC, CMP — assess tolerability, cytopenias, GI/edema

— Monthly CBC until counts stable, then every 3 months

— BCR-ABL1 IS at 3, 6, 9, 12 months and every 3 months thereafter

— CMP, LFTs, lipase every 3 months for first year, then every 6 months

— ECG/QTc at baseline, 7 days after nilotinib initiation, then every 6–12 months

— Lipid panel, HbA1c, BP at baseline and annually (more often on nilotinib/ponatinib)

— Spleen exam and symptom assessment at every visit

— Life expectancy in responsive CP-CML now approaches normal — frame as a chronic disease, not terminal

— Adherence is essential; missed doses translate directly to higher progression risk

— Report new dyspnea, chest pain, calf pain, leg swelling, jaundice, severe diarrhea, bleeding

— Avoid grapefruit juice and unsupervised herbal supplements (St. John's wort)

— Effective contraception if reproductive potential

— Hepatitis B reactivation risk if HBV-exposed

— Encourage physical activity for fatigue and CV risk

— Smoking cessation, weight management

— Mental health screening — adjustment disorder and depression are common in chronic cancer care

— Coordinate with primary care for CV risk, vaccinations, age-appropriate cancer screening

— Clear handoff document when patients move between oncologists or systems — include phase at diagnosis, ELTS, prior TKIs, mutations, PCR trajectory

— Written list of TKI name, dose, timing relative to food, drug interactions to avoid

— Wallet card listing diagnosis and current TKI for emergency providers

Visit and lab schedule for new CP-CML on TKI

Counseling points at diagnosis

Lifestyle and rehab

Transitions of care

Patient education tools

CCS pearl: Schedule the next follow-up visit explicitly on the CCS clock — "BCR-ABL1 PCR in 3 months, hematology clinic, CBC and CMP in 1 month" — Step 3 rewards specific, time-bound monitoring orders.

Board pearl: A patient who skips PCR for a year and presents with rising counts is failing monitoring, not therapy — reinforce surveillance before changing drugs.

Ethical, Legal, and Patient Safety Considerations

— Disclose long-term/lifelong nature of therapy, teratogenicity, drug-specific cardiovascular or pulmonary risks, and financial implications

— Document discussion of alternatives, including TFR potential, and clinical trial options in resistant disease

— Branded TKIs cost $100,000+/year in the US

— Generic imatinib has changed the landscape — off-formulary or non-adherence due to cost is a documented safety event

— Engage social work and pharmacy proactively; document attempts at assistance programs

— Nonadherence is the leading cause of suboptimal response

— Use nonjudgmental, motivational interviewing; do not threaten discontinuation

— Respect patient autonomy in declining TKI (e.g., due to side effects) while documenting the informed refusal and offering alternatives

— Mandatory contraception counseling; document discussion

— Unintended pregnancy on TKI requires non-directive counseling about teratogenicity risk and management options

— Fertility preservation (oocyte/sperm banking) should be offered before TKI initiation in younger patients

— Hospital admissions for unrelated issues are a danger point — TKIs are easily omitted from inpatient medication lists; institute medication reconciliation safeguards and educate patients to advocate

— Perioperative: most TKIs can be held briefly (1–3 days) around surgery with hematology input; long holds risk molecular relapse

— Cancer diagnoses are reportable to state cancer registries (provider responsibility, not patient consent)

— In TKI failure or T315I, clinical trials may offer asciminib combinations or novel agents — ethical obligation to discuss

— Blast phase carries poor prognosis — early goals-of-care discussions, palliative care integration, and advance directive completion before HCT or salvage chemo

Informed consent for TKI therapy

Financial toxicity (uniquely prominent in CML)

Adherence and patient autonomy

Reproductive ethics

Transitions of care risk

Mandatory reporting and registries

Clinical trial enrollment

End-of-life and advanced disease

Step 3 management: When admitting a CML patient for pneumonia, explicitly continue the TKI on the inpatient med list, reconcile with the outpatient pharmacy, and avoid unnecessary holds — TKI omission during hospitalization is a recurring patient-safety pitfall and a high-yield Step 3 trap.

High-Yield Associations and Rapid-Fire Facts

t(9;22)(q34;q11) Philadelphia chromosome → BCR-ABL1 fusion → constitutive tyrosine kinase

Transcripts: p210 (classic CML), p190 (Ph+ ALL, some CML), p230 (CNL-like CML)

Low LAP score, high B12, basophilia, eosinophilia, myelocyte bulge — classic CML quartet

Imatinib = first targeted cancer therapy success story; transformed CML survival

Nilotinib/ponatinib → arterial vascular events; dasatinib → pleural effusion and pulmonary HTN; bosutinib → diarrhea; imatinib → periorbital edema and cramps

T315I mutation → resistant to all TKIs except ponatinib and asciminib

ELTS score is the current preferred risk score in the TKI era

Monitoring is BCR-ABL1 IS on peripheral blood every 3 months; key milestones at 3, 6, 12 months

MMR (MR3) = ≤0.1% IS; MR4 = ≤0.01%; MR4.5 = ≤0.0032%

TFR eligibility: ≥5 yr TKI + ≥2 yr MR4 + reliable monthly PCR

Interferon-alfa is the pregnancy-safe cytoreductive option

Allogeneic HCT reserved for AP/BP, multi-TKI failure, and select pediatric patients

Sokal/Hasford older; ELTS newer — know all three by name

Splenomegaly is the single most useful physical sign in CML

Avoid PPIs with dasatinib/bosutinib (absorption); use famotidine spaced ≥10 h

HBV screening mandatory before TKI; prophylax HBsAg+ patients

All TKIs are CYP3A4 substrates — beware azoles, rifampin, grapefruit

Asciminib = STAMP inhibitor, allosteric myristoyl pocket binder, active in T315I

Hyperleukocytosis treatment: hydration, allopurinol, hydroxyurea, leukapheresis

CML now has near-normal life expectancy in adherent CP responders

Pleural effusion + dasatinib = switch TKI; MI on nilotinib = switch TKI

Step 3 management: When in doubt on a CML vignette, the right next step is almost always "check BCR-ABL1 PCR (IS) and assess adherence" before any drug change.

Board Question Stem Patterns

— 55-year-old with fatigue and LUQ fullness; WBC 145k with basophilia, eosinophilia, myelocyte bulge; spleen 8 cm below costal margin

— Next best step: peripheral blood BCR-ABL1 qPCR (IS); not bone marrow first

— Newly diagnosed CP-CML, prior MI with stent, on aspirin and atorvastatin

— Best choice: imatinib or bosutinib; avoid nilotinib and ponatinib

— 6 months on dasatinib, new dyspnea, right pleural effusion

— Step: hold dasatinib, diurese, consider steroids, switch TKI (imatinib or bosutinib)

— Rising BCR-ABL1 to 2% at 12 months on imatinib

— Next step: assess adherence, send ABL1 kinase domain mutation testing, then switch TKI

— Failed imatinib and dasatinib, mutation testing shows T315I

— Choose: ponatinib (or asciminib); not nilotinib or bosutinib

— Pregnant woman with new CP-CML, WBC 110k

— Manage: interferon-alfa, hydration, allopurinol; defer TKI postpartum; no breastfeeding on TKI

— Patient on imatinib 6 years with stable MR4.5 for 3 years asks to stop

— Next step: TFR trial with monthly BCR-ABL1 PCR; restart if MMR lost

— WBC 320k, confusion, priapism

— Manage: hydration, allopurinol, hydroxyurea, leukapheresis, hematology

— Patient on dasatinib started on omeprazole for GERD

— Step: stop PPI, use famotidine or antacid spaced apart; PPIs reduce dasatinib absorption

— Patient on nilotinib develops claudication

— Step: evaluate for PAD, switch TKI, aggressive CV risk control

Stem 1 — Diagnosis from CBC

Stem 2 — TKI choice with comorbidity

Stem 3 — Pleural effusion on TKI

Stem 4 — Treatment failure with mutation

Stem 5 — T315I mutation

Stem 6 — Pregnancy

Stem 7 — Treatment-free remission

Stem 8 — Hyperleukocytosis with leukostasis

Stem 9 — Drug interaction

Stem 10 — Nilotinib cardiac event

Board pearl: When a stem describes a missed milestone (>10% at 6 months or >1% at 12 months), the correct first action is to confirm adherence and test for ABL1 mutations, then change TKI — premature switching is the trap answer.

Step 3 management: Many CML stems test ambulatory monitoring cadence (3-month PCR) and comorbidity-matched TKI selection — not initial diagnosis.

One-Line Recap

CML is a BCR-ABL1–driven chronic leukemia in which lifelong TKI therapy — selected by patient comorbidity, monitored by quantitative BCR-ABL1 (IS) at 3, 6, and 12 months with ELN milestones, and adjusted for resistance mutations (notably T315I requiring ponatinib or asciminib) — delivers near-normal life expectancy and, in a minority with sustained deep molecular response, the possibility of treatment-free remission.

Diagnose with peripheral BCR-ABL1 qPCR in any adult with unexplained myeloid leukocytosis, basophilia, splenomegaly, and a myelocyte bulge; confirm phase with marrow karyotype and stratify with ELTS.

Match the TKI to the patient: imatinib or bosutinib for cardiovascular disease; avoid nilotinib/ponatinib if vasculopathy; avoid dasatinib if pulmonary disease or anticoagulation; ponatinib or asciminib for T315I.

Monitor relentlessly: BCR-ABL1 IS every 3 months; ≤10% at 3 mo, ≤1% at 6 mo, ≤0.1% (MMR) at 12 mo; missed milestones trigger adherence check and mutation testing before switching.

Plan the long arc: lifelong adherence, cardiovascular secondary prevention, HBV prophylaxis, contraception and pregnancy planning (interferon-alfa in pregnancy), age-appropriate cancer screening, and structured TFR consideration after ≥5 years of TKI and ≥2 years of MR4.

Step 3 management: The exam rewards the candidate who orders the right surveillance lab at the right interval, matches the right TKI to the right comorbidity, and recognizes that nonadherence — not biology — is the most common reason a CML patient deteriorates.