Prospective Study of Patients Treated with Palliative Radiation Therapy While on Immunotherapy

To prospectively document the outcomes of patients treated with palliative radiation therapy (RT) who are receiving immunotherapy.

Patients with advanced cancer receiving or planning to commence immunotherapy within 28 days who were referred for palliative RT at our center between January 2017 and September 2019 were screened for participation in this prospective observational study. Demographic and treatment data, along with patient-reported outcomes (PROs) using the Edmonton Symptom Assessment Scale for cancer, were collected at baseline, after 1 month, and then every 3 months for up to 1 year or until death. RT dose and fractionation were at the discretion of the treating radiation oncologist. Immunotherapy was given as per the standard of care protocol. The primary outcome was 3-month toxicity. Secondary outcomes included response evaluation criteria in solid tumors version 1.1 (RECIST v1.1) response on computed tomography scan performed 1, 3, and 6 months post-RT. The feasibility of enhancing PRO compliance using caregiver-aided PROs and virtual PRO collection was explored.

Thirty-nine patients who received 50 courses of palliative RT (most often for pain) and who also received immunotherapy within 28 days of RT were evaluated for toxicity at 3 months post-RT. The most common primary cancer was non-small cell lung cancer (38%), followed by melanoma (36%). The most common RT dose was 20 Gy in 5 fractions (42%). 87% of patients (34/39) received a programmed cell death protein 1 inhibitor alone. An interval of <14 days between RT and immunotherapy. No grade 3 or higher toxicity was attributable to combined treatment. The median survival for the cohort was 11 months. At 3 months, 26 patients had imaging available for RECIST v1.1; 14 of 26 (54%) had an in-field response, and 3 of 26 (12%) had stable disease (with mixed out-of-field response). Compliance with PROs was 79% (31/39) at 1 month and 69% (27/39) at 3 months. Ten of the 31 patients (32%) and 11 of 31 patients (41%) used caregiver-aided PRO collection.

Palliative RT appears safe in patients receiving immunotherapy with no apparent increase in toxicity because of the combination. Responses out of irradiated volumes were no better than expected than with immunotherapy alone. Caregiver-aided PROs improved compliance with PRO data collection and were feasible.