Survival impact of post-progression chemotherapy in advanced gastric cancer: systematic review and meta-analysis

We conducted a systematic review and meta-analysis on survival impact of post-progression chemotherapy (post-Cx) after first-line chemotherapy (1st-Cx) and after second-line chemotherapy (2nd-Cx), and survival benefit of third-line chemotherapy (3rd-Cx) for advanced gastric cancer (AGC). Phase III trials of systemic chemotherapy for AGC published in English between 2005 and 2015 or presented at annual meetings of ASCO or ESMO between 2013 and 2015 were searched. Numbers of patients, types of chemotherapy, patient baseline, proportion of patients receiving post-Cx (post-Cx%), median progression-free survival (mPFS), and median overall survival (mOS) of each treatment arm were surveyed; trials not reporting these parameters were excluded. Median post-progression survival (mPPS) was calculated as the difference between mOS and mPFS. Weighted Spearman's correlation coefficients between post-Cx% and survival outcomes (mOS and mPPS) were calculated. The effect of post-Cx% on survival outcomes adjusted for the types of chemotherapy and patient characteristics was evaluated by meta-regression. Overall, 25 phase III trials of AGC were selected: 15 trials with 31 arms for 1st-Cx, and 10 trials with 16 arms for 2nd-Cx. Weighted Spearman's correlation coefficients for post-Cx% and mOS/mPPS were 0.520/0.739 for 1st-Cx, and 0.767/0.823 for 2nd-Cx. Meta-regression analyses adjusting for types of chemotherapy, age, and PS showed that a 10% increase in post-Cx% was associated with prolongation of mOS by 1.033 months for 1st-Cx and 0.344 months for 2nd-Cx. Post-Cx% both after 1st-Cx and 2nd-Cx were correlated with mOS/mPPS, suggesting a survival benefit of 3rd-Cx in addition to that of 2nd-Cx for AGC.