EXPRESS: Radiation therapy in combination with immune checkpoint inhibitors in metastatic lung cancer: Effect of fractionation.

Background: Immunotherapy with checkpoint inhibitors has improved the outcomes of patients with metastatic lung cancer in recent years. Despite improved prognosis, not all patients respond to treatment. Therapeutic interventions to build on the success of immune checkpoint inhibitors are needed.

Patients and methods: A retrospective review of patient records for patients who had received immune checkpoint inhibitors in a single cancer center over four years was undertaken. Demographic and disease characteristics of patients with metastatic non-small cell lung cancer were recorded. Data on other treatments including chemotherapy and radiation therapy were extracted, and survival outcomes were calculated.

Results: Most (81.8%) of the 77 metastatic lung cancer patients examined had received palliative radiation therapy within three months of starting immune checkpoint inhibitors. While the survival outcomes of these patients did not differ from patients who had not received radiotherapy, patients who had undergone hypofractionated radiotherapy (defined as one or more fractions of 700 cGy or higher) displayed a better overall survival (OS) than the rest of the cohort.

Conclusion: Palliative radiation therapy administered in proximity with immune checkpoint inhibitors immunotherapy had no effect on the OS of metastatic lung cancer patients. However, patients receiving palliative radiotherapy with fractions above 700 cGy showed better OS. Further studies are needed to optimize a combination strategy.