Helical Skin Radiation Therapy Including Total Skin Radiation Therapy Using Tomotherapy for Primary Cutaneous Lymphoma With Bone Marrow Suppression as a Related Adverse Event

Purpose Total skin electron beam therapy (TSEBT) is useful for primary cutaneous lymphoma. However, helical skin radiation therapy (HSRT) using tomotherapy may avoid the complexity and uncertainty of TSEBT. Methods and Materials All patients with primary cutaneous lymphoma who underwent HSRT at our hospital between June 2015 and July 2019 were investigated, including 7 patients registered in a clinical trial approved by an institutional review board (ID UMIN000022142). HSRT was performed in 3 partitioned skin areas: head and neck, trunk and arms, and legs. Results A total of 24 patients with 53 skin areas (including 8 patients with 24 skin areas who had undergone sequential total skin irradiation), with a median follow-up time of 13 months (range, 2-50), were investigated. Twenty patients (83.3%) had mycosis fungoides (MF). For 41 of 53 (77.4%) cases, a dose of 20 Gy in 10 fractions was used. The overall response rate in the treated fields of each HSRT in patients with MF was 100%, including 38 (80.9%) complete response, 4 (8.5%) good partial response, and 5 (10.6%) partial response. Eight patients with MF who underwent sequential total skin irradiation showed a 100% complete response. For patients with MF, the median survival time after a first round of HSRT was 22 months (95% confidence interval [CI], 13.6-30.4 months), the median response duration of each HSRT was 5 months (95% CI, 3.67-6.32 months), and the median time to in-field reirradiation for each HSRT was 15 months (95% CI, 9.76-20.24 months). Bone marrow suppression (grade ≥3) often occurred (94.1%) with HSRT on trunk and arm skin. An early patient died of HSRT-caused grade 5 leukopenia. Conclusions HSRT targeting trunk and arm skin induced severe bone marrow suppression that led to a temporary palliative effect. TSEBT should still be considered standard treatment for primary cutaneous lymphoma covering the total body surface area.