Abstract
BACKGROUND Cyclooxygenase (COX-2) has been associated with tumor growth and metastasis in several cancers, including thyroid cancer. For this reason, several investigators have studied COX-2 inhibitors in preclinical models of thyroid cancer and found antineoplastic effects. Thus, the primary aim of this study was to assess if the use of nonsteroidal anti-inflammatory drugs (NSAIDs) is associated with a reduced incidence of thyroid cancer. A second aim of the study was to determine additional risk or protective factors for thyroid cancer. METHODS Three large prospective population-based studies (the NIH-AARP Diet and Health Study; the Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial; and the U.S. Radiologic Technologists Study) were pooled to investigate the association between self-reported frequency of aspirin and nonaspirin NSAID use one year prior to baseline (no use, ≤ 2/week, >2-6/week, and ≥ 7/week) and subsequent risk of thyroid cancer. A Cox regression proportional hazard model was used to estimate aggregated hazard ratios (HR) adjusted for cohort, sex, race/ethnicity, weight, smoking status, and alcohol intake. RESULTS There were 388,577 participants in the pooled cohort, with 481 cases of thyroid cancer. No significant risk reduction was observed with regular use of nonaspirin NSAIDs (HR = 1.14 [confidence interval (CI) 0.84-1.55]), and/or regular use of aspirin (HR = 1.06 [CI 0.82-1.39]). The multivariate regression analysis confirmed as previously reported in the literature that female sex, obesity class I (body mass index [BMI] = 30-34.99 kg/m(2)), and obesity class II (BMI = 35-35.99 kg/m(2)) were independently associated with an increased thyroid cancer risk. Current smoking status and moderate and excessive alcohol use were also confirmed as independent risk factors associated with a reduced thyroid cancer risk. CONCLUSIONS Neither nonaspirin NSAIDs nor aspirin use is associated with a reduced risk of thyroid cancer. Women and obesity are associated with an increased risk of thyroid cancer, whereas smoking and alcohol use are associated with decreased risk of thyroid cancer.
