Risk of corticosteroid treatment and hospitalization after checkpoint inhibitor and radiation therapy in patients with cancer

Background Immune checkpoint inhibitors (ICIs) are potent new cancer therapies but can cause serious immune‐related adverse events. ICIs have contributed significantly to improved survival and thereby provide more opportunity for the development of local disease symptomatology requiring palliative radiation. Radiation therapy (RT) has also recently shown benefit in the oligometastatic setting. Data on the interaction and safety of concurrent ICIs and RT are limited. Methods In this retrospective cohort study using a large medical claims database from 2010 to 2017, the need for corticosteroid therapy and the risk of hospitalization within 180 days of treatment with an ICI were determined for patients with a diagnosis of malignant melanoma or lung cancer. Patients were stratified by the use of RT within the 30 days before and after ICI therapy. Results In all, 2020 patients (218 with RT and 1802 without RT) met the inclusion criteria for prednisone analysis, whereas 3519 patients (361 with RT and 3158 without RT) met the inclusion criteria for all other analyses. In a univariable analysis, RT was not associated with the need for prednisone (relative risk [RR], 1.2; 95% confidence interval [CI], 0.8‐1.9) or methylprednisolone (RR, 1.1; 95% CI, 0.7‐2.0). When the end point was hospitalization, RT was significantly associated with hospitalization after ICI therapy for certain cancer/drug combinations (RR for lung cancer/programmed death 1 receptor inhibitors, 1.4; 95% CI, 1.2‐1.6; P < .001; RR for melanoma/ipilimumab, 2.0; 95% CI, 1.0‐3.5; P = .03). Conclusions In patients treated with ICIs, receiving RT was not associated with a higher risk of requiring corticosteroid therapy in comparison with not receiving RT. However, RT was associated with a higher risk of hospitalization, although this finding may be a result of differences in the underlying patient illness severity or oncologic disease burden at the baseline. Lay Summary Data on the interaction of immunotherapy (immune checkpoint inhibitors) and radiation therapy and the safety of combining them are limited. Using a large database, this study has found that patients treated concurrently with immune checkpoint inhibitors and radiation therapy are not at increased risk for requiring corticosteroid therapy (which is used as a proxy for immune‐related adverse events). However, concurrent therapy is associated with a higher risk of hospitalization, although this finding may be due to differences in the underl