The role of radiotherapy in patients with refractory Hodgkin's lymphoma after treatment with brentuximab vedotin and/or immune checkpoint inhibitors

Background: Approximately 10%–30% of patients with Hodgkin's lymphoma (HL) experience relapse or refractory (R/R) disease after first-line standard therapy. Brentuximab vedotin (BV) and immune checkpoint inhibitors (ICIs) have important roles in the salvage treatment of R/R HL. However, subsequent treatment for HL refractory to BV and/or ICI treatment is challenging. Methods: We retrospectively analyzed patients in two institutions who had R/R HL, experienced BV or ICI treatment failure, and received radiotherapy (RT) thereafter. The overall response rate (ORR), duration of response (DOR), progression-free survival (PFS), and overall survival (OS) were analyzed. Results: Overall, 19 patients were enrolled. First-line systemic therapy comprised doxorubicin, bleomycin, vinblastine, and dacarbazine (ABVD, 84.2%); AVD plus ICIs (10.5%); and bleomycin, etoposide, doxorubicin, cyclophosphamide, vincristine, procarbazine, and prednisone (BEACOPP, 5.3%). After first-line therapy, 15 (78.9%) and four patients (21.1%) had refractory disease and relapsed, respectively. After R/R HL diagnosis, six (31.6%), two (10.5%), and 11 (57.9%) patients received BV and ICIs concurrently, BV monotherapy, and ICI monotherapy, respectively. All patients received intensity-modulated RT (n = 12, 63.2%) or volumetric modulated arc therapy (VMAT; n = 7, 36.8%). The ORR as well as the complete response (CR) rate was 100%; the median DOR to RT was 17.2 months (range, 7.9–46.7 months). Two patients showed progression outside the radiation field; one patient had extensive in-field, out-of-field, nodal, and extranodal relapse. With a median follow-up time of 16.2 months (range, 9.2–23.2 months), the 1-year PFS and OS were 84.4% and 100%, respectively. PFS was associated with extranodal involvement (P = 0.019) and gross tumor volume (P = 0.044). All patients tolerated RT well without adverse events of grade ≥ 3. Conclusion: RT is effective and safe for treating HL refractory to BV or ICIs and has the potential to be part of a comprehensive strategy for HL.