3741 - Safety and Efficacy of Five Fraction Hypofractionated Radiotherapy in Aggressive Lymphomas
Presenter(s)
Y. P. Wang1, C. C. Baniel1, S. Richter1, J. B. Ross2, R. T. Hoppe1, M. S. Binkley1, and S. M. Hiniker1; 1Department of Radiation Oncology, Stanford University School of Medicine, Stanford, CA, 2Department of Radiation Oncology, Stanford Cancer Institute, Stanford, CA
Purpose/Objective(s): Hypofractionated radiotherapy (hypoRT) may be particularly useful in the setting of relapsed/refractory and aggressive lymphoma where higher doses are optimal for local control, but data remain limited. This study aims to retrospectively evaluate the safety and efficacy of a 5 fraction hypoRT regimen in treating patients with aggressive lymphoma.
Materials/Methods: We retrospectively identified patients aged >18 years with aggressive lymphoma treated with hypoRT (dose >2.2Gy per fraction) between 2021-2023. Aggressive lymphomas were defined by histology, including diffuse large B cell lymphoma (DLBCL), mantle cell lymphoma, Hodgkin lymphoma, anaplastic large cell lymphoma, or peripheral T cell lymphoma. Patients with indolent lymphoma, mycosis fungoides, or those who received radiation as a bridging treatment for CAR-T therapy were excluded. We measured baseline characteristics, CTCAE v5.0 acute toxicity, radiotherapy details, and anatomic site. Objective response rate to treated lesions was assessed by PET/CT or clinical examination (ORR, partial or complete response at 6 months). Kaplan-Meier was used to determine freedom from local progression (FFLP) and disease progression free survival (PFS).
Results: Fifteen patients received hypoRT from 2021-2023 representing 27 unique treatment sites. Of the 15 patients, the median age was 70 (range:34-88), with 60% male. Histologies included DLBCL (n=6), anaplastic large cell lymphoma (n=3), and mantle cell lymphoma (n=2), B cell lymphoma -NOS (n=2), Hodgkin Lymphoma (n=1), and T cell lymphoma -NOS (n=1). Initial staging data reflects 2 stage IA, 1 stage IIIA, and 8 stage IV; 12 patients (80.0%) presented with relapsed/recurrent disease. Of the 27 treatment sites, 5 were bone, 6 lymph nodes, 13 cutaneous, and 3 visceral. All patients received 5 fraction treatment to either 20.5Gy, 24Gy, or 27.5Gy total dose per institutional protocol. Median EQD2(10) was 29.6Gy (24.1-35.5Gy) and median BED10 was 35.5 (28.9-42.6). Grade 1 dermatitis was the most common acute treatment toxicity (n=2/15) followed by grade 1 fatigue (n=1/15) and grade 2 esophagitis (n=1/15) with no acute grade 3+ toxicities. The ORR at 6 months was 100% with all sites exhibiting a partial or complete response. At a median follow up of 11.5 months (1, 44), n=1/27 sites exhibited local failure yielding a FFLP of 96% for all courses. Of note, this patient experienced out of field progression at 2 months after treatment with stable disease in the treated site, but ultimately progressed in-field 8 months after hypoRT in the context of overall disease progression. PFS at 1 year was 47% and 1 year OS was 73%.
Conclusion: A 5 fraction hypoRT regimen for aggressive lymphoma was well tolerated with no grade 3 acute toxicity and excellent objective response rates and freedom from local progression, even in the setting of overall disease progression.