Background
Retrospective multi-institution cohort study. 90 patients with myeloid sarcoma (chloroma/granulocytic sarcoma) — isolated extramedullary presentation or concurrent with AML/MDS/MPN. Evaluated outcomes of RT (given as primary treatment for isolated disease or as adjunct to chemotherapy) and the role of consolidative RT in preventing local relapse after chemotherapy. PMID 21962486 (Bakst RL et al, IJROBP 2011).
Interventions and follow up
Arm A: RT ± systemic chemotherapy (dose range: 20–36 Gy for definitive/consolidative RT; 24–30 Gy for most sites)
Primary endpoint: Local control, OS, conversion to AML
mFollow up: 2.5 year
Primary endpoint: Local control, OS, conversion to AML
mFollow up: 2.5 year
Results
Arm B (comparison): Systemic chemotherapy alone (historical controls)
Local control (RT ± chemo): 75% vs chemotherapy alone ~40%, P<.01
2-yr OS: 48% (RT + chemo) vs 25% (chemo alone) — trend favoring RT
Conversion to AML (isolated MS without upfront AML chemo): 100% at 5 years regardless of RT
Local control (RT ± chemo): 75% vs chemotherapy alone ~40%, P<.01
2-yr OS: 48% (RT + chemo) vs 25% (chemo alone) — trend favoring RT
Conversion to AML (isolated MS without upfront AML chemo): 100% at 5 years regardless of RT
Adverse events
Main adverse events: RT: site-dependent — CNS (somnolence, neurocognitive), orbit (dry eye, cataracts), mediastinum (esophagitis, pneumonitis), spinal cord (neuropathy, myelopathy risk), abdominal (GI toxicity). At standard doses (<36 Gy) toxicity generally acceptable.
Conclusions
RT provides excellent local control for myeloid sarcoma and may improve OS when combined with systemic AML-type chemotherapy. Isolated myeloid sarcoma should be treated with AML-type induction chemotherapy, not RT alone, as conversion to systemic AML is universal without systemic therapy. RT has a role as consolidation or for emergent management of symptomatic disease.
Key Limitations
Key Limitations: Retrospective, heterogeneous patient population. Selection bias in who received RT. AML-induction chemotherapy was not uniformly delivered. Allogeneic SCT (for eligible patients) confounds long-term outcomes. Definition of "isolated" myeloid sarcoma may have been inconsistent across centers.
Clinical Context
Current standard for isolated myeloid sarcoma: AML-type induction chemotherapy ± RT for local control of symptomatic or bulky disease, followed by allogeneic SCT in eligible patients. RT 24–30 Gy is recommended for emergent cord compression, orbit, or other symptomatic sites. RT alone without systemic therapy is inadequate given universal systemic progression.
References