Analgesic use and the risk of kidney cancer: a meta-analysis of epidemiologic studies.

Analgesics are the most commonly used over-the-counter drugs worldwide with certain analgesics having cancer prevention effect. The evidence for an increased risk of developing kidney cancer with analgesic use is mixed. Using a meta-analysis design of available observational epidemiologic studies, we investigated the association between analgesic use and kidney cancer risk. We searched the MEDLINE and EMBASE databases to identify eligible case-control or cohort studies published in English until June 2012 for three categories of analgesics: acetaminophen, aspirin or other non-steroidal anti-inflammatory drugs (NSAIDs). Study-specific effect estimates were pooled to compute an overall relative risk (RR) and its 95% confidence interval (CI) using a random-effects model for each category of the analgesics. We identified 20 studies (14 with acetaminophen, 13 with aspirin and five with other NSAIDs) that were performed in six countries, including 8,420 cases of kidney cancer. Use of acetaminophen and non-aspirin NSAIDs were associated with an increased risk of kidney cancer (pooled RR: 1.28; 95% CI: 1.15-1.44 and 1.25; 95% CI: 1.06-1.46, respectively). For aspirin use, we found no overall increased risk (pooled RR: 1.10; 95% CI: 0.95-1.28), except for non-US studies (five studies, pooled RR: 1.17; 95% CI: 1.04-1.33). Similar increases in risks were seen with higher analgesic intake. In this largest meta-analysis to date, we found that acetaminophen and non-aspirin NSAIDs are associated with a significant risk of developing kidney cancer. Further work is needed to elucidate biologic mechanisms behind these findings.