A 55-year-old man is diagnosed with chronic myelomonocytic leukemia (CMML) with 8% blasts in bone marrow and monosomy 7 cytogenetics. He is transfusion-dependent and symptomatic. Which agent is the preferred first-line treatment?

Explanation

## First-Line Treatment of CMML **Key Point:** Azacitidine is the preferred first-line hypomethylating agent (HMA) for symptomatic CMML, particularly in patients with adverse cytogenetics (monosomy 7) or high blast burden, based on landmark trials and international guidelines. ### CMML: Classification and Treatment Rationale CMML is a myelodysplastic/myeloproliferative neoplasm (MDS/MPN overlap) with: - Persistent monocytosis (>1,000/µL) - 0–19% blasts in bone marrow - Often associated with adverse cytogenetics (monosomy 7, trisomy 8) - High risk of transformation to acute myeloid leukemia (AML) **High-Yield:** CMML with monosomy 7 is considered high-risk; hypomethylating agents (azacitidine or decitabine) are the standard of care, offering superior survival compared to supportive care or cytoreductive agents. ### Comparison of First-Line Agents | Agent | Mechanism | Response Rate | Median OS | Dosing | Role in CMML | |-------|-----------|---------------|-----------|--------|---------------| | **Azacitidine** | DNA methyltransferase inhibitor | 40–50% | 14–20 months | 75 mg/m² × 7 days/month | **First-line HMA** | | Decitabine | DNA methyltransferase inhibitor | 35–45% | 12–18 months | 20 mg/m² × 5 days/month | Alternative HMA | | Hydroxyurea | Ribonucleotide reductase inhibitor | 20–30% | 8–10 months | Oral, variable | Cytoreduction only | | Imatinib | BCR-ABL1 TKI | <5% | N/A | Not applicable | No role (CMML is BCR-ABL1-negative) | **Clinical Pearl:** Azacitidine is preferred over decitabine in CMML because: 1. Azacitidine has dual mechanisms: DNA methylation inhibition AND direct cytotoxicity 2. Azacitidine can be given subcutaneously or IV; decitabine is IV only 3. Azacitidine has a longer half-life, allowing monthly dosing (vs. 5-day cycles for decitabine) ### Treatment Goals in CMML - Reduce monocytosis and organomegaly - Improve cytopenias and transfusion dependence - Delay or prevent AML transformation - Improve quality of life and median overall survival **Warning:** Hydroxyurea provides only temporary cytoreduction and does not alter disease biology; it is not recommended as first-line therapy for CMML with adverse risk factors. **Mnemonic:** **AZA-CMML** = Azacitidine is the first-line HMA for CMML.