Efficacy of trastuzumab beyond progression in HER2 positive advanced gastric cancer: a multicenter prospective observational cohort study

INTRODUCTION: Trastuzumab plus chemotherapy is the standard first-line regimen in HER2 positive advanced gastric cancer (AGC), but lack of data in post-progression treatment. So, it is worth evaluating the efficacy of continuing trastuzumab after failure of the first-line trastuzumab based treatment. METHODS: 59 patients were enrolled from Zhongshan Hospital Fudan University, Sun Yat-sen University Cancer Center and Peking University Cancer Hospital between September 2012 and Oct 2015. Patients were divided into two groups according to the second line regimens: with or without trastuzumab. The primary endpoint was progression free survival of second line therapy (PFS2). Secondary end points included overall survival (OS), response rate, and adverse events (AEs). RESULTS: Baseline factors were well balanced between two groups. 32 patients treated with trastuzumab plus second line chemotherapy (group A) and 27 patients received chemotherapy alone (group B). The median follow-up time was 7.60 months (range 1.50-32.50). Longer median PFS2 was observed in group A than in group B (3.1 vs 2.0 months, P=0.008). There was no significant differences of median OS2 calculating from the second line therapy (10.5 vs 6.5 months, P=0.172) between two groups. Response rate was 9.3% in group A compared with 3.7% in group B (P=0.617). AEs were similar in two groups including cardiac safety. Subgroup analysis showed that factors of male, age<65, good performance status, HER2 immunohistochemical (IHC) 2+ and poor response to first line indicated superior PFS2 in patients continuing trastuzumab to those treated with chemotherapy alone. CONCLUSION: Continuing treatment of trastuzumab beyond first line therapy progression showed effective and safe in AGC.