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Background: Regular use of aspirin reduces the risk of a colorectal neoplasm, but the mechanism by which aspirin affects carcinogenesis in the colon is not well understood. Methods: We estimated cyclooxygenase-2 (COX-2) expression by immunohistochemical assay of sections from paraffin-embedded colorectal-cancer specimens from two large cohorts of participants who provided data on aspirin use from a questionnaire every 2 years. We applied Cox regression to a competing-risks analysis to compare the effects of aspirin use on the relative risk of colorectal cancer in relation to the expression of COX-2 in the tumor. Results: During 2,446,431 person-years of follow-up of 82,911 women and 47,363 men, we found 636 incident colorectal cancers that were accessible for determination of COX-2 expression. Of the tumors, 423 (67%) had moderate or strong COX-2 expression. The effect of aspirin use differed significantly in relation to COX-2 expression (P for heterogeneity=0.02). Regular aspirin use conferred a significant reduction in the risk of colorectal cancers that overexpressed COX-2 (multivariate relative risk, 0.64; 95% confidence interval [CI], 0.52 to 0.78), whereas regular aspirin use had no influence on tumors with weak or absent expression of COX-2 (multivariate relative risk, 0.96; 95% CI, 0.73 to 1.26). The age-standardized incidence rate for cancers that overexpressed COX-2 was 37 per 100,000 person-years among regular aspirin users, as compared with 56 per 100,000 person-years among those who did not use aspirin regularly; in contrast, the rate for cancers with weak or absent COX-2 expression was 27 per 100,000 person-years among regular aspirin users, as compared with 28 per 100,000 person-years among nonregular aspirin users. Conclusions: Regular use of aspirin appears to reduce the risk of colorectal cancers that overexpress COX-2 but not the risk of colorectal cancers with weak or absent expression of COX-2. N Engl J Med 2007;356:2131-42. [ABSTRACT FROM AUTHOR]

Background: More information is needed about the long-term effects of low-dose aspirin (≤160 mg) on incident hepatocellular carcinoma, liver-related mortality, and gastrointestinal bleeding in persons with chronic hepatitis B or hepatitis C virus infection.Methods: Using nationwide Swedish registries, we identified all adults who received a diagnosis of chronic hepatitis B or hepatitis C from 2005 through 2015 and who did not have a history of aspirin use (50,275 patients). Patients who were starting to take low-dose aspirin (14,205 patients) were identified by their first filled prescriptions for 90 or more consecutive doses of aspirin. We constructed a propensity score and applied inverse probability of treatment weighting to balance baseline characteristics between groups. Using Cox proportional-hazards regression modeling, we estimated the risk of hepatocellular carcinoma and liver-related mortality, accounting for competing events.Results: With a median of 7.9 years of follow-up, the estimated cumulative incidence of hepatocellular carcinoma was 4.0% among aspirin users and 8.3% among nonusers of aspirin (difference, -4.3 percentage points; 95% confidence interval [CI], -5.0 to -3.6; adjusted hazard ratio, 0.69; 95% CI, 0.62 to 0.76). This inverse association appeared to be duration-dependent; as compared with short-term use (3 months to <1 year), the adjusted hazard ratios were 0.90 (95% CI, 0.76 to 1.06) for 1 to less than 3 years of use, 0.66 (95% CI, 0.56 to 0.78) for 3 to less than 5 years of use, and 0.57 (95% CI, 0.42 to 0.70) for 5 or more years of use. Ten-year liver-related mortality was 11.0% among aspirin users and 17.9% among nonusers (difference, -6.9 percentage points [95% CI, -8.1 to -5.7]; adjusted hazard ratio, 0.73 [95% CI, 0.67 to 0.81]). However, the 10-year risk of gastrointestinal bleeding did not differ significantly between users and nonusers of aspirin (7.8% and 6.9%, respectively; difference, 0.9 percentage points; 95% CI, -0.6 to 2.4).Conclusions: In a nationwide study of patients with chronic viral hepatitis in Sweden, use of low-dose aspirin was associated with a significantly lower risk of hepatocellular carcinoma and lower liver-related mortality than no use of aspirin, without a significantly higher risk of gastrointestinal bleeding. (Funded by the National Institutes of Health and others.). [ABSTRACT FROM AUTHOR]

Background: Regular use of aspirin after a diagnosis of colon cancer has been associated with a superior clinical outcome. Experimental evidence suggests that inhibition of prostaglandin-endoperoxide synthase 2 (PTGS2) (also known as cyclooxygenase-2) by aspirin down-regulates phosphatidylinositol 3-kinase (PI3K) signaling activity. We hypothesized that the effect of aspirin on survival and prognosis in patients with cancers characterized by mutated PIK3CA (the phosphatidylinositol-4,5-bisphosphonate 3-kinase, catalytic subunit alpha polypeptide gene) might differ from the effect among those with wild-type PIK3CA cancers. Methods: We obtained data on 964 patients with rectal or colon cancer from the Nurses' Health Study and the Health Professionals Follow-up Study, including data on aspirin use after diagnosis and the presence or absence of PIK3CA mutation. We used a Cox proportional-hazards model to compute the multivariate hazard ratio for death. We examined tumor markers, including PTGS2, phosphorylated AKT, KRAS, BRAF, microsatellite instability, CpG island methylator phenotype, and methylation of long interspersed nucleotide element 1. Results: Among patients with mutated-PIK3CA colorectal cancers, regular use of aspirin after diagnosis was associated with superior colorectal cancer–specific survival (multivariate hazard ratio for cancer-related death, 0.18; 95% confidence interval [CI], 0.06 to 0.61; P<0.001 by the log-rank test) and overall survival (multivariate hazard ratio for death from any cause, 0.54; 95% CI, 0.31 to 0.94; P=0.01 by the log-rank test). In contrast, among patients with wild-type PIK3CA, regular use of aspirin after diagnosis was not associated with colorectal cancer–specific survival (multivariate hazard ratio, 0.96; 95% CI, 0.69 to 1.32; P=0.76 by the log-rank test; P=0.009 for interaction between aspirin and PIK3CA variables) or overall survival (multivariate hazard ratio, 0.94; 95% CI, 0.75 to 1.17; P=0.96 by the log-rank test; P=0.07 for interaction). Conclusions: Regular use of aspirin after diagnosis was associated with longer survival among patients with mutated-PIK3CA colorectal cancer, but not among patients with wild-type PIK3CA cancer. The findings from this molecular pathological epidemiology study suggest that the PIK3CA mutation in colorectal cancer may serve as a predictive molecular biomarker for adjuvant aspirin therapy. (Funded by The National Institutes of Health and others.) [ABSTRACT FROM PUBLISHER]