Effectiveness of low-dose radiation for primary cutaneous anaplastic large cell lymphoma.

Purpose: Primary cutaneous anaplastic large cell lymphoma (pcALCL) is conventionally treated with radiation therapy (RT) doses ≥30 GGy, but effectiveness of lower doses is unclear. We compared responses after a range of RT doses for pcALCL.

Methods and materials: From 1999 through 2015, 45 lesions in 21 patients met clinicopathologic pcALCL diagnostic criteria and were treated with RT (<20 Gy, 20-29 Gy, or ≥30 Gy dose). Complete clinical (CR) and partial responses (PR) were compared by dose using Fisher exact test. Progression-free and overall survivals were calculated using the Kaplan-Meier method.

Results: Forty-two percent of lesions were treated with <20 Gy, 22% with 20 to 29 Gy, and 35% with ≥30 Gy. Within 12 weeks, 100% responded, with 67% CR and 33% PR; by last follow-up, 87% achieved CR and 13% PR (no difference by RT dose; P = .84). Three-year freedom from local relapse was 100%, 86%, and 100% with <20 Gy, 20 to 29 Gy, and ≥30 Gy, respectively ( P = .28). Many patients ultimately demonstrated other cutaneous or systemic relapse, with 55% 3-year and 29% 10-year progression-free survival. Overall survival at 10 years was 59%, with 2 deaths from complications of disease.

Conclusions: Low-dose RT offered excellent local control in the setting of the indolent, chronic course of pcALCL in this patient cohort.