Unconventional radiotherapy to enhance immunotherapy efficacy in bulky tumors: a case report.

Determining the most appropriate management strategy for patients with large tumor masses is a very challenging issue. Unconventional radiotherapy modalities, such as spatially fractionated radiation therapy (SFRT), are associated with dramatic responses. Recent studies have suggested that systemic immune activation may be triggered by SFRT delivery to primary tumor lesion. This report describes the case of a patient treated with a novel form of immune-sparing partially ablative irradiation (ISPART) for a bulky peritoneal metastasis from renal cell cancer, refractory to anti-PD-1 therapy (nivolumab) as third-line therapy after sequential therapy with sunitinib and cabozantinib. The observed response suggests that there may be a synergistic effect between ISPART and immunotherapy. This case report supports the inclusion of ISPART in patients presenting with bulky lesions treated with checkpoint inhibitors .