OVER-THE-COUNTER ANALGESICS AND RISK OF OVARIAN-CANCER

Background Evidence that aspirin and other non-steroidal anti-inflamma tory drugs reduce risk for colorectal cancer has prompted interest in their ability to prevent other cancers. We aimed to find out what effe ct over-the-counter analgesics have on risk of ovarian cancer. Methods In a case-control study we compared use of over-the-counter analgesic s by 563 women from eastern Massachusetts and New Hampshire, USA, who had epithelial ovarian cancer with 523 women from the general populati on. We calculated exposure odds ratios to estimate the effect of over- the-counter analgesics on ovarian cancer risk. Use of over-the-counter analgesics was assessed through interviews and defined as use al leas t once a week continuously for at least 6 months. Findings The odds ra tio for risk of ovarian cancer for aspirin use was 0.75 (95% CI 0.52-1 .10), that for ibuprofen was 1.03 (0.64-1.64), and that for paracetamo l was 0.52 (0.31-0.86), after adjusting for age, study centre, educati on, religion, parity, oral contraceptive use, and menstrual, arthritic , or headache pain. Relative to no use, the lower risk of ovarian canc er associated with paracetamol was more apparent for use on a daily ba sis, 0.39 (0.21-0.74), for more than 10 years of use, 0.40 (0.19-0.88) , or for more than 20 tablet years defined as (tablets per dayXyears o f use), 0.45 (0.20-0.99). Interpretation In our data, there was a stat istically significant inverse association between paracetamol use and ovarian cancer risk. There was a modest but nonsignificant inverse ass ociation with aspirin use and ovarian cancer and no association with i buprofen use. Experimental studies in rodents demonstrating uterine an d ovarian atrophy at high doses of paracetamol and decreased ovarian-c yst formation at lower doses suggest a biological basis for our observ ations.