Impact of Double- or Triple-Hit Pathology on Rates and Durability of Radiation Therapy Response Among Patients With...

Double-hit lymphomas and triple-hit lymphomas (DHL/THL), also known as high-grade B-cell lymphoma with MYC and BCL2 or BCL6 rearrangements, are associated with chemoresistance and inferior survival. However, whether radiation therapy (RT) efficacy is altered in DHL/THL is less well characterized. Among patients with relapsed or refractory large B-cell lymphoma (R/R LBCL), we compared rates and durability of response between patients with and without DHL/THL.

We retrospectively reviewed consecutive R/R LBCL patients who were irradiated at a single institution from January 2008 to June 2017. Patients in whom c-MYC rearranged status was known were evaluated for response to RT, in-field control, progression-free, and overall survival.

Among 245 irradiated patients with LBCL, 41 patients with confirmed c-MYC status were treated for R/R disease (14 DHL/THL, 27 non-DHL/THL) and formed our cohort. Compared with non-DHL/THL, more DHL/THL patients had progressive disease at RT (71% vs 48%), had larger gross tumor volumes (GTV; median 696 mL vs 117 mL), and were treated with palliative intent (71% vs 41%). Despite similar RT doses (median 35 Gy), radiographic complete response rate was lower among DHL/THL patients: 14.3% versus 64.7% (P = .01). With a median 2 years of follow-up, one in-field failure was observed in each group. DHL/THL patients had inferior progression-free survival (7% vs 46%; P = .02) and overall survival (14% vs 68%; P = .03) at 6 months.

R/R LBCL is responsive to RT, although rates of response are lower among DHL/THL patients. Given poor survival after RT, in-field control was hard to evaluate in this cohort. Larger cohorts are required to better elucidate whether differences in response rates are driven by larger disease burden at RT versus tumor biology. These findings are of increasing pertinence in light of use of RT as bridging therapy to cellular immunotherapies.