Toxicity of sequential immune therapy and radiation for cervical and thoracic spine metastases.

Abstract

130 Background: Palliative radiation is an effective treatment modality for spinal metastases. Expanding use of immune therapy in metastatic cancer raises concern that side effects from treatment may be exaggerated, particularly to sensitive organs such as the esophagus. This retrospective review evaluates the toxicity of combined radiation and immune therapy in patients with cervical or thoracic spine metastases. Methods: Patients receiving radiation for cervical or thoracic spine metastases from 2012-2017 were selected based on (1) concurrent use of immune therapy and radiation (within 7 days) OR radiation within 30 days following immune therapy, (2) 3D conformal or simpler treatment technique, and (3) minimum 30 days follow up from end of treatment. Patient demographics, radiation treatment parameters, immune therapy agent(s), and maximum toxicity were extracted from the medical record. Isoeffective dose was calculated using the EQD2 model, assuming α/β of 3. Statistical analyses included t tests. Results: Twenty-two patients were identified. Pembrolizumab was most commonly combined with radiation (8 patients), followed by nivolumab (7), ipilimumab (3), and atezoliumab (2). Two patients received both nivolumab and ipilimumab. Three patients (14%) had grade 3 toxicity requiring hospitalization (vomiting, esophagitis), 8 patients (36%) had grade 2 toxicity (esophagitis, dysphagia), 3 patients (14%) had grade 1 toxicity (hoarseness, dysphagia), 8 patients (36%) had no toxicity. Two patients (67%) with grade 3 toxicity received concurrent nivolumab and ipilimumab. Median dose was 3600 cGy (EQD2) in 10 fractions. There was a trend to greater toxicity with increased number of vertebral levels treated (mean 3.4, 4.6, 5.625 and 6.3 for toxicity grade 0, 1, 2 and 3, respectively; p= 0.053). Dose, fractionation, and immune therapy agent were not found to be significant contributors. Conclusions: In this small cohort, combined immune therapy and radiation for palliation of cervical or thoracic spine metastases suggests increased toxicity when greater number of vertebral bodies are irradiated or when combined immune therapy agents are utilized. Further investigation with a larger cohort is warranted.