1517PImpact of radiotherapy on efficacy of anti-programmed death 1 (PD-1) antibodies in metastatic NSCLC

Abstract Background The impact of radiotherapy (RT) on the efficacy and toxicity of immune checkpoint inhibitors in patients (pts) with metastatic non-small cell-lung cancer (NSCLC) is unclear. Methods We retrospectively identified pts with metastatic NSCLC treated with the anti-programmed death 1 (PD-1) antibodies nivolumab or pembrolizumab between January 2016 and May 2019 at two major oncology centres in Melbourne, Australia. Patient demographics, tumour characteristics, treatment history including radiotherapy (RT) use and toxicity were collected. Disease control rate (DCR), progression free survival (PFS) and overall survival (OS) were analysed and correlated with RT use. Results 132 pts identified with interim analysis of 54 reported here. Median follow up was 19.4 months. Majority were male (61%) and 87% were smokers. 80% had non-squamous histology, of these 9% had an EGFR mutation. Brain metastases were present in 41%. The median number of cycles of anti-PD1 treatment received was 5 and only 7% started anti-PD-1 as first-line therapy. 36% received RT treatment either during or within 3 months of starting anti-PD1 treatment. Of patients that received RT, 74% were treated with extra-thoracic RT. The use of RT before or during anti-PD1 treatment did not result in an increase in high grade immune-related adverse events. The DCR was 35%. The median PFS was 2 months (95% CI 0.5 – 29) and OS 9.7 months (95% CI 1.0 – 31). Pts who received RT had a numerically shorter PFS than those that did not (1.5 vs 2 months, p = 0.668) but numerically longer OS (8.1 vs 7.2 months, p = 0.857). Updated analysis with the full cohort and with longer follow-up will be presented. Conclusions Radiotherapy did not significantly impact on survival in pts with metastatic NSCLC treated with anti-PD1 therapy. Legal entity responsible for the study The authors. Funding Has not received any funding. Disclosure All authors have declared no conflicts of interest.