Success of Ultra-low Dose Radiation Therapy for Primary Cutaneous B-cell Lymphoma.

Objectives: Primary cutaneous B-cell lymphoma (PCBCL) is a relatively rare disease, associated with 5-year overall survival of nearly 95% when treated with external beam radiation therapy (EBRT) alone. However, standard EBRT doses yield acute skin toxicity in more than 70% of patients and grade 3 to 4 acute skin toxicity in nearly 10% of patients. Consequently, the PCBCL treatment paradigm is shifting towards lower EBRT doses. This study evaluates our early experience with ultra-low dose EBRT (total dose of 4 Gy in 2 fractions) for PCBCL.
Methods: Four biopsy-confirmed PCBCL lesions (1 anterior thigh and 3 chest) in 2 male patients were treated with 2 Gy×2 fraction EBRT using electrons through a clinical setup. The anterior thigh lesion was treated using a clamshell to protect the scrotum from scatter dose. Treatment was achieved using 9 MeV electrons to the 85% isodose line using no bolus, with follow-up every 4 months and potential retreatment if no visible response at 8 to 9 months.
Results: All lesions demonstrated a response to EBRT by 4 months, visibly manifesting as flattening with changes in pigmentation. At the last follow-up (20, 20, 16.5, and 4 mo, respectively), all lesions had flattened with no evidence of local recurrence and no skin toxicity.
Conclusions: Treatment of PCBCL with ultra-low dose EBRT to 4 Gy total dose in 2 fractions provides durable local control with zero skin toxicity. These results are encouraging for both the success of treatment and the potential to use similarly low doses for retreatment should patients exhibit local recurrence.
Competing Interests: S.M. serves as a consultant for Gilmartin Capital (a company that evaluates surgically targeted radiation therapies) and receives research funding from the University Hospitals Minority Faculty Career Development Award, the Robert Winn Diversity in Clinical Trials Career Development Award (sponsored by the Bristol Myers Squibb Foundation), the Case Comprehensive Cancer Center Accelerator Pilot Project Award, the Gilead Sciences Research Scholars Program in Solid Tumors Award, and the Susan G Komen Career Catalyst Research Grant. The remaining author declares no conflicts of interest.
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