Outcomes in primary cutaneous diffuse large B-cell lymphoma, leg type.

Primary cutaneous diffuse large B-cell lymphoma, leg type (PCDLBCL, LT) is a rare, aggressive lymphoma characterized by skin involvement predominantly in the lower extremities. Immunochemotherapy with or without involved-site radiation therapy (ISRT) is considered standard front-line therapy. Over-expression of PD-L1/PD-L2 is seen in a high proportion of PCDLBCL, LT cases, but efficacy of immune checkpoint inhibitors (ICI) in relapsed/refractory, PCDLBCL, LT has not been thoroughly studied. We conducted a retrospective cohort study of patients diagnosed with PCDLBCL, LT seen at Mayo Clinic from 1 January 2000 to 31 December 2020. Using the Kaplan-Meier method, we calculated progression-free survival, duration of response, and overall survival in patients who received front-line rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP) with and without ISRT, and salvage ICI therapy for relapsed/refractory disease. A total of 28 patients with PCDLBCL, LT were identified. The median PFS in patients treated with R-CHOP plus ISRT was 58 months (95% CI: 18-112) compared to 14 months (95% CI: 5-not reached; p = 0.04) in those treated with R-CHOP without ISRT. The median PFS from salvage ICI therapy was 10 months (95% CI: 4-not reached), and median DOR from salvage ICI therapy was 23 months [95% CI: 4-26]. R-CHOP with ISRT had a significantly longer median PFS compared to R-CHOP without ISRT as front-line therapy for PCDLBCL, LT. ICIs may have a role in treating relapsed/refractory disease as reasonable activity in heavily pre-treated patients was observed in this study.