Risk of Gastric and Colorectal Cancer After Tamoxifen Use for Breast Cancer A Systematic Review and Meta-Analysis

Objective:It is still controversial whether tamoxifen use for breast cancer will simultaneously cause gastric and colorectal cancer. In this study, we aimed to evaluate the association between tamoxifen use and the risk of gastric and colorectal cancer by performing a systematic review and meta-analysis.Materials and Methods:A comprehensive literature search for relevant studies published from 1969 to October 2013 was performed in PubMed, MEDLINE, and ISI Web of Science. Only articles in which gastric and colorectal cancer was reported after tamoxifen therapy for breast cancer were included. Pooled relative risk (RR) estimates and 95% confidence intervals (CIs) were calculated using both the random-effects and fixed-effects models.Results:We found a total of 9 studies that met the inclusion criteria for the analysis of tamoxifen use and incidence of gastric and colorectal cancer. Among these studies, 7 were involved with both gastric and colorectal cancer, 1 with gastric cancer and 1 with colorectal cancer. The random-effects model results showed that tamoxifen use for breast cancer was not a risk factor for either gastric cancer (RR=0.92; 95% CI, 0.41-2.07, P=0.84) or colorectal cancer (RR=1.05; 95% CI, 0.90-1.21, P=0.54). Sensitivity analysis indicated that the duration or dose of tamoxifen use had no effect on these 2 gastrointestinal tumors (P>0.05). Stratified analysis showed that tamoxifen use was not associated with the increased risk of gastric and colorectal cancer regardless of whether the latency interval after breast cancer diagnosis was <5 or 5 years.Conclusion:Our meta-analysis results indicate that there was no substantial increase in gastric and colorectal cancer among the tamoxifen-treated female patients.