Outcomes of immunomodulatory radiation strategies in combination with nivolumab compared with single agent nivolumab in lung cancer patients.

e21134 Background: In advanced non- small cell lung cancer, when compared with Docetaxel, the absolute improvement in one- year overall survival (OS) with nivolumab monotherapy (Checkmate 017 and 057) is a modest 12- 18%. Preclinical studies have demonstrated improved response rates with combined PD- 1 blockade and ablative radiation. Hence, it has been our programmatic approach to combine nivolumab with stereotactic ablative radiotherapy to symptomatic metastatic sites. However, the optimal fractionation and timing of radiation with nivolumab are unclear. Here we examine the OS, incidence of toxicities and the timing of radiation in lung cancer patients who received nivolumab and external beam radiotherapy (iEBRT), nivolumab and stereotactic ablative radiotherapy (iSABR) and nivolumab monotherapy. Methods: All lung cancer patients who started nivolumab between April 2015 and May 2017 were identified by retrospective chart review. Patients who received EBRT or SABR 3 months before initiating nivolumab or during nivolumab therapy were identified. Follow up cut off date was 31 December, 2017. Kaplan Meier analysis was used to estimate OS. Results: Out of 109 advanced lung cancer patients who received nivolumab, 30 received iSABR and 13 received iEBRT. Seventeen patients received SABR in the 3 months preceding initiation of nivolumab (Before) and 13 received SABR during nivolumab therapy (Sandwich). All 13 patients who received EBRT did so in the 3 months preceding the initiation of nivolumab. Median follow up time was 18.5 months. No statistically significant difference was found in the incidence of grade 3-4 adverse events between different groups (χ2(2) = 4.2, p = 0.25). There were no grade 5 adverse events. Survival estimates are as follows- Conclusions: This review of our programmatic approach, demonstrates a 29% absolute improvement in 18- month OS with iSABR Sandwich when compared to nivolumab monotherapy and no OS improvement with EBRT given prior to initiation of nivolumab. Group 18-month OS (%) mOS (95% CI) (months) Log rank p = 0.02 iSABR Sandwich 41.6 16.4 (8.8- 22.0) iSABR Before 18.5 8.6 (5.1- 15.0) iEBRT 7.7 3.9 (1.4- 11.4) Nivolumab monotherapy 12.5 5.4 (2.8- 7.8)