Extent of skin involvement as a prognostic indicator of disease free and overall survival of patients with T3 cutaneous T-cell lymphoma treated with total skin electron beam radiation therapy

BACKGROUND. The goal of this study was to define the prognostic significance of the extent of skin involvement (ESI) with respect to disease free survival (DFS) and overall survival (OS) of patients with T3 cutaneous T-cell lymphoma (CTCL) after total skin electron beam therapy (TSEBT). METHODS, Between 1974 and 1993, TSEBT (36 Gray [Gy], 1 Gy/day for 9 weeks, 6 MeV electrons) was administered to a total of 213 patients. Forty-six of the 213 patients were classified as having T3 CTCL based on the presence of tumor nodules on the skin at diagnosis. Patient records were evaluated retrospectively, and the percentage of total skin surface involved was calculated. Patients were analyzed with respect to response to therapy, disease free and overall survival. The median follow-up was 37.5 months (range, 1.6-93 months). RESULTS, Thirty-six of 46 patients achieved complete clinical response (CCR) by the completion of TSEBT. DFS was 12% at 36 months with approximately 28% OS. When stratified by extent of skin involvement, 100% of patients with 9% or less ESI were disease free at 18 months compared with patients with 10% or greater ESI, all of whom had relapsed by 18 months (78% achieved CCR). Fifty percent of those with 9% or less ESI remained disease free at 36 months; median DFS and OS were not reached at 63 and 65 months, respectively. The median DFS and OS for the 10% or greater ESI group were 4 and 24 months, respectively. These differences were statistically significant (P less than or equal to 0.005). Toxicity of therapy was minimal. CONCLUSIONS, The extent of skin involvement of patients with T3 CTCL is a prognostic indicator of disease free and overall survival for those who have been treated definitively with TSEBT.