Does taking aspirin really reduce risk for prostate cancer-specific mortality?

Posted on October 27, 2010 by Sitemaster

A presentation to be given next week at the upcoming annual meeting of the American Society for Radiation Oncology (ASTRO) will suggest that men initially diagnosed with localized prostate cancer and who take an anti-clotting agent are at significantly lower risk for prostate cancer-specific death at 10 years of follow-up.

A regular aspirin regimen has previously been linked to a reduction in risk of developing colon cancer, although this is still not definitive. In the study to be reported by Choe and colleagues next week, they will present data suggesting that men taking aspirin or some other anti-clotting agent (e.g., warfarin or enoxoparin [Lovenox] or clopidogrel [Plavix]) may have a > 50 percent reduction in relative risk for prostate cancer-specific mortality. However, even the research team emphasizes that these are preliminary findings from a retrospective analysis. Newly diagnosed prostate cancer patients are not being encouraged to start an immediate regimen of daily aspirin in the hope that it will extend their lives.

It is already well know that (a) people with cancer are more prone to blood clots; (b) people with blood clots have a higher risk of cancer; and (c) laboratory and animal studieshave shown that anti-clotting agents can affect the growth and spread of cancer. So Choe and his colleagues decided to test the idea that anti-clotting drugs might affect the risk of death among men with prostate cancer.

According to a media release from ASTRO, their study was based on an analysis of data from 5,275 men initially diagnosed with localized cancer who were enrolled in the CaPSURE data registry. The data from these men have been reported (in an article on WebMD) to show the following:

• 1,982/5,275 men (34.6 percent) were taking anti-clotting agents.
• At 10 years of follow-up
  • 10 percent of men not taking an anti-clotting agent had died from prostate cancer.
  • 4 percent of men taking an anticlotting agent had died of prostate cancer.
  • 7 percent of men not taking an anti-clotting agent had metastasis.
  • 3 per cent of men taking an anti-clotting agent had metastasis.
  • 43 percent of men not taking an anti-clotting agent had prostate cancer recurrence.
  • 33 percent of men taking an anti-clotting agent had prostate cancer recurrence.

While these data show a relative risk reduction of 50 percent in prostate cancer-specific mortality (from 10 to 4 percent), the absolute risk reduction is only 6 percent.

Anthony Zietman, MD, the president of ASTRO, says that these data need to be confirmed, and that even if they are confirmed, the optimal dose, timing, and duration of use of the anti-clotting agent would still need to be worked out. However, Dr. Choe points out that those ”patients who are taking aspirin for other reasons may see an added benefit.”

Aspirin and other anti-clotting agents are well known to carry risks for internal bleeding and related complications. Even a daily “mini-aspirin” (a dose of just 75 mg/day) is not without risk. Patients should not start to self-medicate with any anti-clotting agent without first discussing this with their doctor.