Efficacy of chemotherapy for patients with unresectable or recurrent pancreatic adenosquamous carcinoma: A multicenter retrospective analysis

647 Background: Pancreatic adenosquamous carcinoma (PASC) is a rare variant of pancreatic ductal adenocarcinoma (PDAC). Although unresectable or recurrent PASC is usually treated by systemic chemotherapy, there are few reports which show the efficacy of chemotherapy. The aim of this study was to evaluate the efficacy of chemotherapy for patients (pts) with unresectable or recurrent PASC. Methods: We collected data retrospectively from 24 Japanese institutions. The selection criteria were as follows: 1) histologically or cytologically proven PASC (non-surgical specimens were eligible if squamous cell carcinoma (SCC) was detected), 2) unresectable or recurrent disease treated with 1st line chemotherapy between April 2001 and December 2017. Results: This study included 138 pts with median age of 66 years (range: 36-85). About 60% of pts were diagnosed with biopsy and only SCC was detected in 13.0% of pts. Median overall survival (mOS) was 6.7 months (M), median progression free survival (mPFS) was 2.8 M, and the 1-year survival rate (1YSR) was 26.7%. For the 102 metastatic or distal recurrent pts with PS of 0-1, patient characteristics were as follows: ≥76 years old, 9 (8.8%); PS of 0, 39 (38.2%); number of metastatic sites ≥2, 25 (24.5%). The treatment efficacies (The objective response rates(%)/mPFS(M)/mOS(M)/1YSR(%)) of the 5 major regimens were Gemcitabine(GEM) (n=45, 4.4%/2.2M/4.8M/28.1%), GEM+nab-PTX (n=24, 29.2%/2.9M/7.6M/23.1%), GEM+S-1 (n=9, 11.1%/5.1M/9.9M/25.4%), FOLFIRINOX (n=7, 14.3%/2.5M/7.5M/14.3%), and S-1 (n=7; 28.6%/2.6M/5.0M/28.6%), respectively. One patient with liver metastasis underwent conversion surgery after GEM+nab-PTX and achieved long survival. CRP ≥3.0mg/dl, CA19-9 ≥1000 U/ml, residual primary site, and monotherapy had a significant correlation with poor survival in multivariate analysis. Conclusions: Although combination chemotherapy regimens such as FOLFIRINOX and GEM+nab-PTX are now available, the prognosis of metastatic PASC remains poor. Development of more effective treatment options is required.