Efficacy and toxicity of hypofractionated radiation therapy for patients with hematologic malignancies: update on a COVID era ILROG collaborative report

Abstract

Purpose/Objectives: During COVID19, shorter radiation therapy (RT) courses were considered to minimize patient exposure, ensure staff safety, and conserve healthcare resources. Due to concerns with the safety of systemic therapy, RT demands were also increased. In response, guidelines were published by the International Lymphoma Radiation Oncology Group (ILROG) to guide the treatment of hematologic malignancies patients with hypofractionated radiation therapy (hRT) regimens. These guidelines suggested hRT dose/fractionation schemes based on the known radiosensitivity of various hematologic malignancies with consideration of the biologically equivalent doses in the hRT setting. However, the outcomes for these dose/fractionation regimens in terms of efficacy and toxicity are unknown. Materials/Methods: In collaboration with ILROG, we performed a retrospective multinational, multicenter study. We included any patient treated from 1/1/2020 to 8/31/2020 with hRT given according to the published ILROG guidelines or hRT given at >3 Gy per fraction. We abstracted patient and treatment data from the respective institutional databases. CTCAE v5.0 was used to grade toxicity. Results: We included 237 patients from 8 different institutions treated with 282 RT courses. Patient and treatment details are reported in Table 1. Median RT dose was 12 Gy (range 4–39) in a median of 3 fractions (range 1–13). Median follow up was 181 days, with 174 patients (73%) alive at last follow up. Response within the RT field was assessed in 228 sites: complete response (CR) (n = 143, 63%); partial response (PR) (n = 59, 26%); stable disease (SD) (n = 15, 7%); and progressive disease (PD) (n = 11, 5%). Maximal toxicities reported were Grade 1 (n = 45), Grade 2 (n = 24), Grade 3 (n = 4) and Grade 4 (n = 1). Grade 3 toxicities occurred with the following treatment regimens: 12 Gy in 3 fx to extremity (dermatitis, given concurrent with methotrexate); 30 Gy in 6 fx to extremity (dermatitis); 20 Gy in 5 fx to pelvis (pain); 25 Gy in 5 fx to abdomen (pain). One grade 4 toxicity occurred with 12 Gy in 3 fx to the CNS (hematologic toxicity). Conclusions: Treatment of hematologic malignancies patients with hRT was generally well tolerated with few unexpected toxicities. Evaluation of efficacy is limited by patient and treatment heterogeneity but appears to be reasonable. These data can provide guidance for emergency situations requiring minimization of patient and staff exposure. Perhaps more importantly, hRT could be considered even in routine settings to spare patients time on treatment, especially for certain patient subgroups. Keyword: Radiation Therapy Conflicts of interests pertinent to the abstract. U. Ricardi Consultant or advisory role: Advisory Board member and Speaker Honoraria: Astra Zeneca Research funding: Institutional Research Cooperation: Accuray, BrainLab L. Specht Consultant or advisory role: Takeda, Kyowa Kirin, MSD Honoraria: Takeda Research funding: Varian, ViewRay, Danish Cancer Society