Do common pain medications mask signs of prostate cancer?

A study recently published in the journal Cancer has suggested that common painkillers such as paracetamol and aspirin might affect blood levels of a marker commonly used to diagnose prostate cancer.

In this study, Singer et al. examined levels of prostate specific antigen (PSA) in the bloodstream of 1,319 men aged over 40 years. PSA is a protein produced in the prostate gland. Blood levels of PSA will be minuscule in healthy men, but raised levels often indicate the presence of prostate cancer. If a simple blood test detects serum levels of PSA higher than a specific threshold (4 ng/ml to be exact), your doctor will be booking you in for a digital rectal examination with a prostate cancer specialist faster than you can say "He wants to stick his finger where?!"

In addition, study participants were asked how often they took analgesic drugs classed as non-steroidal anti-inflammatory drugs (NSAIDs) - common types being aspirin and ibuprofen - or the drug acetaminophen, which you'll probably be familiar with as paracetamol. NSAIDs and acetaminophen act as painkillers by reducing inflammation. Given that inflammation in the prostate has been implicated in the development of prostate cancer, the authors of this study wanted to find out whether NSAIDs or acetaminophen affected the risk of prostate cancer in men who took these drugs.

The results of this study showed that serum levels of PSA in men who took NSAIDs or acetaminophen "nearly every day" were considerably lower than levels in men who did not take either drug. Seeing as this study didn't then follow these men for several years to find out whether there were fewer instances of prostate cancer in the men who took these analgesics than in those who didn't, it is not clear whether this decrease in PSA levels means that the drugs reduce the risk of cancer. In fact, it it possible that NSAIDs and acetaminophen may reduce serum levels of PSA despite suspicious goings on in the prostate and thus cause doctors to miss cases of prostate cancer, which would otherwise be flagged by raised PSA levels.

So what are the implications of the study? Should men chew down aspirin every day to prevent prostate cancer, or would they make detection of the malignancy more difficult for their doctor by doing so? Dr Eric Singer, one of the authors of this study, told Reuters news, "If you're a guy who's close to the upper limit of normal [in PSA levels] or would have been over the upper limit and now you're under it because of [these drugs], that could certainly change whether or not you would be referred for a biopsy [to check for a tumor]". He also emphasizes that these findings are preliminary and shouldn't prompt men to change their behaviour.

----------------------------------------------------------------------------------------
Eric A. Singer, Ganesh S. Palapattu, Edwin van Wijngaarden (2008). Prostate-specific antigen levels in relation to consumption of nonsteroidal anti-inflammatory drugs and acetaminophen Cancer DOI: 10.1002/cncr.23806