P1.01-63 Impact of Prior Radiation Pneumonitis on Incidence of Immunotherapy Related Pneumonitis

Abstract

Patients with a history of radiation pneumonitis (RP) requiring steroids have generally been excluded from immuno-oncology (IO) trials of PD-1/PDL-1 monoclonal antibodies for safety concerns. The risk of IO-associated pneumonitis (IOP) in this group of patients (pts) is therefore unknown. We evaluated the frequency of IOP in pts who had prior RP. We evaluated all pts with non-small cell lung carcinoma (NSCLC) treated at our institution between 2011 and 2018 who were diagnosed with RP and at a later point received IO. Demographics, tumor characteristics, steroid use and outcomes were extracted from the electronic medical record. Median overall survival (mOS), median progression free survival (mPFS), and median time to treatment failure (mTTF) from the start of IO were estimated from Kaplan-Meier curves. We identified 29 pts: median age at diagnosis 63 yrs, 51.7% male, none had received prior targeted therapies. IO treatments were: atezolizumab (2), durvalumab (2), nivolumab (12), and pembrolizumab (13). Median time from RP diagnosis to start of IO was 14.2mo (2.2-75 mo). 23 pts (79%) had experienced prior grade ≥2 RP requiring steroids. Only 2 of the 29 pts (6.9%) developed IOP. Both pts had required steroids for prior RP and both received durvalumab; one pt was on prednisone ≥10mg at the start of IO. Both required steroid treatment of IOP, are still on IO and have not progressed (censored at 8.3mo and 9.9mo). OS and PFS after IO are similar (Table 1) whether or not pts required treatment for RP or were on prednisone ≥ 10 mg (or steroid equivalent) at the start of IO.Table 1IO outcomes based on RP history and steroid use at start of IORP Grade ≥ 2 n=23 (95% CI)RP Grade < 2 n=6 (95% CI)Prednisone ≥ 10mg n=7 (95% CI)Prednisone < 10mg n=22 (95% CI)All patients n = 29 (95% CI)mPFS (mo)5.44 (2.1-12.6)12.95 (0.95-)6.16 (2-)5.44 (2.1-)6.16 (2.4-)mOS (mo)6.6 (3.93-13.8)NR14.3 (5.3-)8 (3.4-16.8)8 (5.3-15)mTTFa (mo)2.3 (1.9-4.8)2.3 (1.9-)4.4 (2-)2.3 (1.9-10.9)2.75a (2-7)an=28: 1 pt lost to follow up after start of IO Open table in a new tab an=28: 1 pt lost to follow up after start of IO In our cohort, the incidence of IOP after RP is low and similar to the rate of pneumonitis reported with pembrolizumab in pts with prior exposure to thoracic radiation.