Hormone replacement therapy and nonsteroidal anti -inflammatory drugs on the risk of colorectal cancer in women.

Nonsteroidal anti-inflammatory drugs (NSAIDs) and hormone replacement therapy (HRT) are each associated with a 30% to 50% reduction in risk of colorectal cancer based on separate studies. To investigate the use of both NSAID and HRT and risk of colorectal cancer, we conducted a nested case-control study from a cohort of women aged 40 and older who belonged to a medical group practice patient population. Cases (N=539) were newly diagnosed colorectal cancers that occurred between 1991 and 2003. Controls (N=1255) were matched to cases by age (+/-2 years) and insurance enrollment status with at least two controls per case. Exposure data were collected from pharmacy claims databases and medical records. Logistic regression was used to calculate the odds of colorectal cancer associated with HRT and NSAIDs use. Overall, 24.7% of cases and 32.8% of controls were exposed to HRT, 36.6% of cases and 40.7% of controls were exposed to prescription NSAIDs. Ever use of HRT was associated with a reduced risk of colorectal cancer (adjusted Odds Ratio (OR) = 0.72; 95% confidence interval (CI): 0.55-0.94). The effect of HRT use remained the same regardless of duration or timing of use during the study period. Ever NSAID use was associated with a reduced risk of colorectal cancer (adjusted OR = 0.87; 95%CI: 0.69-1.11). NSAID use greater than one year of duration (adjusted OR = 0.54; 95%CI: 0.33-0.87) and within 6 months of diagnosis (OR = 0.56; 95% CI: 0.33-0.93) were also associated with a decreased risk of colorectal cancer. Ever use of both HRT and NSAIDs and risk of colorectal cancer was significantly associated with a reduced risk of colorectal cancer (adjusted OR = 0.53; 95%CI: 0.34-0.82). However, there was no evidence of either a synergistic or antagonistic effect between HRT and NSAIDs (p for interaction = 0.31). In conclusion, timing and duration of use were influential only for NSAIDs, but these factors did not alter the effect of HRT on colorectal cancer risk. Women who had ever used both NSAIDs and HRT were less likely to develop colorectal cancer compared to women who used only NSAIDs or HRT.Ph.D.Health and Environmental SciencesPublic healthUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/126202/2/3238003.pd