Singh, Siddharth

Abstract Physical activity may be associated with reduced risk of gastric cancer. We performed a systematic review and meta-analysis to evaluate the magnitude of the association and the quality of supporting evidence. After a comprehensive search of bibliographic databases and conference proceedings through February 2013 for observational studies that examined associations between recreational and/or occupational physical activity and gastric cancer risk, we identified 16 studies (seven cohort, nine case control) reporting 11,111 cases of gastric cancer among 1,606,760 patients. Summary adjusted-OR estimates with 95% confidence intervals (CI) were estimated using the random-effects model. Meta-analysis demonstrated that the risk of gastric cancer was 21% lower among the most physically active people as compared with the least physically active people (OR = 0.79; 95% CI, 0.71–0.87) with moderate heterogeneity among studies (I2 = 55%). This protective effect was seen for gastric cancers in the cardia (four studies; OR = 0.80; 95% CI, 0.63–1.00) and distal stomach (five studies; OR = 0.63; 95% CI, 0.52–0.76). The effect size was significantly smaller in high-quality studies (six studies; OR = 0.86; 95% CI, 0.75–0.99), as compared with low-quality studies (10 studies; OR = 0.74; 95% CI, 0.69–0.81). The results were consistent across sex, study quality, study design, and geographic location. In conclusion, meta-analysis of published observational studies indicates that physical activity is associated with reduced risk of gastric cancer. Lifestyle interventions focusing on increasing physical activity may decrease the global burden of gastric cancer, in addition to a myriad of other health benefits. Cancer Prev Res; 7(1); 12–22. ©2013 AACR.

Abstract Background: Antidiabetic medications (ADM) may modify colorectal cancer risk in patients with diabetes mellitus. We performed a systematic review and meta-analysis, evaluating the effect of metformin, thiazolidinediones (TZD), sulfonylureas, and insulin on colorectal cancer risk in diabetic patients. Methods: We conducted a systematic search of multiple bibliographic databases, up to September 2012, for articles that evaluated exposure to metformin, TZD, sulfonylureas, and insulin, reported colorectal cancer risk in patients with diabetes mellitus, and reported OR or provided data for their estimation. Summary OR estimates with 95% confidence intervals (CI) were estimated using the random-effects model. Results: Fifteen studies reporting 13,871 cases of colorectal cancer in 840,787 patients with diabetes mellitus were included. Meta-analysis of observational studies showed an 11% reduction in colorectal cancer risk associated with metformin use (n = 9 studies; OR, 0.89; 95% CI, 0.81–0.99), whereas TZD use was not associated with colorectal cancer risk (n = 5 studies; OR, 0.96; 95% CI, 0.87–1.05). Conversely, a trend toward higher colorectal cancer risk was observed with sulfonylurea (n = 7 studies; OR, 1.11; 95% CI, 0.97–1.26) and insulin (n = 9 studies; OR, 1.33; 95% CI, 0.91–1.94) use, although these associations were not statistically significant. There was considerable heterogeneity across studies, partly explained by study location and adjustment for concomitant use of other ADMs. Post-hoc analysis of randomized controlled trials did not reveal any significant association between ADM and colorectal cancer risk. Conclusions: Meta-analysis of published studies supports a protective association between metformin use and colorectal cancer risk in patients with diabetes mellitus. Impact: Clinical trials on the chemopreventive effect of metformin against colorectal cancer are warranted. Cancer Epidemiol Biomarkers Prev; 22(12); 2258–68. ©2013 AACR.