Abstract 1640: Class switch or identical regimen as a second-line chemotherapy for patients with metastatic gastric adenocarcinoma: A retrospective analysis of two medical centers in Taiwan
Authors: Bai Li-Yuan , Kuo Yung-Chia , Chen Jen-Shi , Chou Wen-Chi , Chiu Chang-Fang , Liao Yu-Min 
Published: August 2018

Abstract
Introduction: Background: Chemotherapy with a fluoropyrimidine with or without a platinum is currently the standard care for metastatic gastric cancer (GC). Randomized trials have established the role of either a taxane- or an irinotecan-containing regimen as second line chemotherapy. However, medical insurance systems don't permit the reimbursement of both taxane and irinotecan in some countries, including Taiwan. Patients who fail the first line chemotherapy in Taiwan usually receive a regimen containing a fluoropyrimidine / platinum different from the prior regimen, or a self-paid regimen containing paclitaxel, docetaxel or irinotecan. The impact of selecting an identical vs. a class switch chemotherapy on the outcomes of patients is not known.
Procedures: The medical records of patients who were diagnosed with metastatic gastric adenocarcinoma from 2008 to 2012 and had received a second line chemotherapy after a first line regimen of fluoropyrimidine (5-fluorouracil, UFT, capecitabine or S-1), and/or platinum (cisplatin, carboplatin or oxaliplatin) were retrospectively obtained from two medical centers in Taiwan. In a second line situation, we defined an identical regimen as a regimen containing another fluoropyrimidine with or without a platinum; and a class switch regimen as a regimen containing paclitaxel, docetaxel or irinotecan. The characteristic and clinical outcomes of the two groups of patients were compared. Kaplan-Meier curves were used to demonstrate the progression free survival (PFS) and overall survival (OS) function of each treatment group. All reported p values were two-sided with the alpha set at a significance of 0.05.
Findings: A total of 201 patients met the study criteria. Patients in the identical regimen group were older (p=0.001) and were less likely to stop first line treatment due to disease progression (PD; p=0.026) compared to the class switch group. Although the response rates (CR+PR) were similar (7.8% vs. 8.3%), toxicity occurred more frequently in identical group than in class switch group by 5%. The survival outcomes measures for the identical regimen group and class switch group included 9 and 6.8 weeks (p=0.949) median PFS since second line treatment, 16 and 12 weeks (p=0.585) median OS since second line treatment, and 48 and 58 weeks (p=0.457) median OS since disease diagnosis, respectively.
Conclusions: Patients receiving an identical chemotherapy after failure of a fluoropyrimidine with/without a platinum regimen have similar PFS and OS compared to patients receiving a class switch chemotherapy for GC. A higher percentage of PD as the reason to stop first line therapy was noted in patients receiving a class switch chemotherapy and might influence the assessment of a class switch regimen. Further prospective clinical trials are needed to clarify this potential confounding factor.
Citation Format: Li-Yuan Bai, Yung-Chia Kuo, Jen-Shi Chen, Wen-Chi Chou, Chang-Fang Chiu, Yu-Min Liao. Class switch or identical regimen as a second-line chemotherapy for patients with metastatic gastric adenocarcinoma: A retrospective analysis of two medical centers in Taiwan [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1640.