Background: In the phase 3 PACIFIC trial of unresectable, stage III NSCLC patients (pts) without progression after concurrent chemoradiotherapy (cCRT), durvalumab (durva) significantly improved PFS and OS with similar safety compared to placebo (pbo). We performed exploratory analyses to characterize first subsequent treatment (Tx) after discontinuation of durva. Methods: Pts with WHO PS 0/1 and any tumor PD-L1 status were randomized (2:1) 1–42 days after ≥2 cycles of platinum-based cCRT to durva 10 mg/kg IV or pbo Q2W up to 12 months, stratified by age, sex and smoking history. Pts were classified by the use or not of first subsequent Tx and category of first systemic Tx (platinum doublet CT [PDCT], single-agent CT [SCT], immunotherapy [IT] or targeted therapy [TT]). Results: As of Mar 22, 2018, 216/476 (45.4%) and 153/237 (64.6%) in the durva and pbo arms, respectively, had a RECIST-based PFS event per BICR (5.7% and 8.4% due to death). 195 (41.0%) and 128 (54.0%) received first subsequent Tx, most of which were systemic Tx (158 [33.2%] and 109 [46.0%]): PDCT (16.4% and 19.0%), SCT (8.6% and 8.4%), IT (4.2% and 13.5%) or TT (3.8% and 5.1%); 7.8% and 8.0% received RT only. Time to first subsequent therapy or death (TFST) was longer with durva vs pbo (HR 0.58; 95% CI 0.47–0.72; median 21.0 vs 10.4 months). Baseline characteristics of pts with or without first subsequent Tx were similar, and similar across durva or pbo arms. Among pts with systemic Tx, baseline characteristics (including pre-cCRT PD-L1 status) were generally similar, except pts on TT, more of whom were EGFR+ (70.0% vs 0–6.6% of other systemic Tx groups) with commonly associated phenotypes (more females, Asians, non-smokers and non-squamous pts). Best overall response to first systemic Tx will be presented. Conclusions: Due to longer PFS and fewer progression events with durva vs pbo, fewer pts on durva required subsequent Tx and, per TFST, much later. With the exception of IT, use of each subsequent Tx was similar between the durva and pbo arms with PDCT the most common. Baseline characteristics were similar for pts with or without first subsequent Tx and pts who received first systemic Tx, except for pts who received TT, as expected due to their molecular profile.