Stereotactic and hypofractionated radiotherapy associated with immune checkpoint inhibitor drugs. Analysis of local control, toxicity, and outcome in a single research centre case study

Background/Aim: We evaluated local control and toxicity in patients receiving radiotherapy associated with immune check point inhibitors and analyzed which oligometastatic disease setting benefits the most from local ablation in terms of advantage in overall survival. Patients and Methods: We retrospectively identified 60 oligoprogressive patients treated with a PD-1 inhibitor in association with radiotherapy on the site of progression (119 lesions). Results: After a median follow-up of 11.7 months (range=1-39 months), we observed complete response (CR) in 45/119, partial response (RP) in 42/119, and stable disease (SD) in 30/119 patients. Nine radionecrotic events occurred. Two patients experienced grade 3 toxicities and 32 patients reported grade 2 toxicities. The number of radiologically evident metastatic organs in patients who received concomitant PD-1 inhibitors and radiotherapy showed a significant increase in survival (respectively, 73% after 12 months and 47% after 24 months) in patients with 0-3 metastatic organs compared to those with more than 3 organ sites involved (p<0.0001). Conclusion: Radiotherapy associated with PD-1 inhibitors is overall safe and efficacious. Patients eligible for intensification of local treatments should have less or equal to 3 metastatic organ sites.