Safety of Concurrent Systemic Therapy and Total Skin Electron Therapy in Cutaneous T-Cell Lymphoma

To evaluate the safety and outcomes of total skin electron therapy (TSET) delivered with concurrent systemic therapy (CS) for cutaneous T-cell lymphoma (CTCL).

We retrospectively identified CTCL patients (including Sézary syndrome and mycosis fungoides) receiving TSET from 2013 to 2023. Acute toxicities were graded per CTCAE v5.0 and defined as new or worsened (N/W) from baseline. Cutaneous response was assessed at 2-8 weeks and 6 months post-TSET. Analyses of toxicity and response were performed per TSET course and classified as CS if any systemic agent was administered during treatment. Survival outcomes were estimated using Kaplan-Meier methods in per-patient analyses using one index course per patient, with time measured from the start of TSET.

A total of 121 TSET courses were analyzed, including 75 (62%) with CS and 46 (38%) without concurrent systemic therapy (NCS). Median follow-up was 21 months overall and longer for CS courses (28 vs. 16 months; P = .019). Nearly all courses experienced ≥1 N/W toxicity, most of which was low grade. High-grade toxicities occurred in 13% of CS and 26% of NCS courses (P = .080), with no grade ≥4 events. Overall, toxicity burden and symptom outcomes were similar between groups. Toxicity severity appeared comparable across commonly used systemic therapy classes; one patient receiving concurrent methotrexate experienced disproportionate toxicity. Early overall response rates at 2-8 weeks were 90% (CS) and 92% (NCS) (P = .138). In per-patient analyses, median progression-free survival was 8.61 versus 6.08 months (log-rank P = .325), and 24-month overall survival was 85.7% versus 68.3% (log-rank P = .098) for CS and NCS, respectively.

TSET can be delivered safely with most commonly used CS therapies in CTCL.