152 Background: The efficacy of anti-PD-1 antibody for metastatic gastric cancer (mGC) was revealed. In non-small cell lung cancer (NSCLC), it was reported that overall response rate (ORR) in patients (pts) treated with chemotherapy (CTx) after immunotherapy exposure was higher than historical data from the pre-anti-PD-(L)1 era. The purpose of this retrospective study was to evaluate whether CTx improved efficacy outcomes after exposure anti-PD(L)1 antibody in mGC. Methods: We investigated retrospectively clinical characteristics at baseline of mGC pts who received CTx after progression of anti-PD-(L)1 antibody between April 2014 and August 2017. Anti-PD-(L)1 antibody was adapted as third- or later-line therapy. Pts fulfilled following criteria: histologically proven adenocarcinoma; ECOG PS 0-2; adequate organ functions; and received CTx including fluoropyrimidines (FU), platinum, and taxane or irinotecan. We evaluated efficacy outcomes, including ORR, disease control rate (DCR), time to treatment failure (TTF), and overall survival (OS). Results: Out of 40 treated with anti-PD-(L)1 antibody, 15 pts were included. Patient characteristics were as follows: median age (range), 67 (46-83) years; male/female, 13/2; ECOG PS (0/1/2), 5/8/2; HER2 positive, 8; histology (differentiated/undifferentiated), 10/5; metastatic lesions (peritoneum/liver/lung), 4/8/3; number of metastatic sites (1/≥2), 2/13; number of prior CTx regimens (3/4/5), 2/9/4; median period (range) from first line CTx, 30.7 (12.7-68.1) months; and CTx regimens (FU+oxaliplatin/taxane/irinotecan), 10/3/2. ORR, DCR, median TTF, and OS were 33% (95% CI, 15.2-58.3), 87% (95% CI, 62.1-96.3), 3.5 (95% CI, 1.6-4.4) months, and 7.6 (95% CI, 4.4-8.5) months, respectively. There were no predictive and prognostic factors associated with ORR, TTF, and OS on univariate analysis. At the beginning of CTx, 4 pts had immune-related adverse events (irAEs), but these were manageable and no new irAEs appeared during CTx. Conclusions: Our data support further evaluation of the use of CTx after progression of anti-PD-L 1 antibody, even in heavily pretreated mGC pts. Updated results will be presented.
P-355 Trastuzumab-based treatment of HER2-positive metastatic gastric cancer
