Nonsteroidal anti-inflammatory drugs and subsite-specific colorectal cancer incidence in the Iowa women's health study.
BACKGROUND
Previous epidemiologic studies have shown that regular use of nonsteroidal anti-inflammatory drugs (NSAIDs) is associated with decreased colorectal cancer risk. However, few studies have examined associations between NSAID use and subsite-specific colorectal cancer risks. Because tumors of the proximal and distal colon differ with respect to their genetic alterations, clinicopathologic features, and demographic distribution, further investigation of subsite-specific colorectal cancer risks may be rewarding.


METHODS
Data about aspirin and non-aspirin-NSAID use were recorded by self-report in 1992 among the initially cancer-free cohort of postmenopausal women in the Iowa Women's Health Study (n = 27,160). In total, 637 women developed colorectal cancer during the 11 years of follow-up, including 365 proximal colon, 132 distal colon, and 120 rectal cancer cases (11 overlapping and 9 not specified).


RESULTS
For colon cancer, the multivariable-adjusted hazard ratios (HR) for women reporting use of aspirin two to five times and six or more times weekly (compared with nonusers of aspirin) were 0.79 [95% confidence interval (95% CI), 0.59-1.04] and 0.76 (95% CI, 0.58-1.00), respectively. The corresponding HRs for non-aspirin NSAIDs were 0.63 (95% CI, 0.41-0.96) and 0.85 (95% CI, 0.63-1.15), respectively. For proximal colon cancer, the multivariable-adjusted HRs for women reporting use of aspirin or non-aspirin NSAIDs two or more times weekly (compared with nonusers of each) were 0.67 (95% CI, 0.51-0.87) and 0.71 (95% CI, 0.52-0.97), respectively. No statistically significant association was found between either distal colon or rectal cancer and aspirin or non-aspirin NSAID use.


CONCLUSIONS
Our study is consistent with a limited number of prior reports that have observed stronger associations between NSAID use and proximal versus distal colorectal cancer.
Mahipal
Amit
A
Division of Epidemiology and Community Health, School of Public Health, University of Minnesota, 1300 South Second Street, Minneapolis, MN 55454, USA.
Anderson
Kristin E
KE
Limburg
Paul J
PJ
Folsom
Aaron R
AR
D000368:Aged; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000627:therapeutic use*; D001241:Aspirin / Q000627:therapeutic use; D003110:Colonic Neoplasms / Q000453:epidemiology* / Q000517:prevention & control; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D007484:Iowa / Q000453:epidemiology; D008875:Middle Aged; D017698:Postmenopause; D016016:Proportional Hazards Models; D011446:Prospective Studies; D012004:Rectal Neoplasms / Q000453:epidemiology* / Q000517:prevention & control; D012307:Risk Factors; D011795:Surveys and Questionnaires; D013997:Time Factors
D000894:Anti-Inflammatory Agents, Non-Steroidal; D001241:Aspirin