Recent findings from a study sponsored by the National Cancer Institute (NCI) suggest that men may not need to have a PSA test as often as previously thought. Depending on how low the PSA level is at the time of initial testing, repeat testing may not be necessary for up to five years.

The PSA test measures the level of prostate-specific antigen in the blood and is widely used to screen for prostate cancer, a disease that kills 30,000 men each year in this country. Although PSA levels in the blood may be elevated with benign conditions, such as an enlarged prostate, elevated levels are also a potential indicator of this deadly form of cancer. Leading organizations, such as the American Cancer Society and the American Academy of Family Physicians, do not fully agree about the usefulness of the PSA test for saving lives; these organizations find even less agreement about how often it should be performed (see Screening Adults/Prostate cancer and Screening Adults 50+/Prostate cancer).

The NCI study is helping to address these issues, particularly the latter. The just-released data come from NCI’s Prostate, Lung, Colorectal and Ovarian (PLCO) trial, a large study in which nearly 30,000 male patients were randomized to receive either annual PSA testing and digital rectal exams or “usual care” as determined by their regular doctors.

A PSA level over 4 nanograms per milliliter of fluid has been a common benchmark for cause for concern. Results from the PLCO trial indicate that for men with PSA levels below 1 nanogram, 98.7% will still have a level below 4 nanograms up to 4 years later. Even among men with slightly elevated PSA values, between 1.1 and 2 nanograms, 98.8% are likely to have an acceptable PSA level the next year. Therefore, the study suggests that annual PSA testing may not be necessary for all men over 50.

Instead, researchers concluded that a more appropriate testing regimen would be every 5 years for men with PSA levels under 1 nanogram and every other year for those with PSA levels between 1.1 and 2 nanograms. However, for men with a PSA value between 2 and 4 nanograms, study investigators recommend continuing with yearly testing.

These results provide additional data for medical professionals and organizations to consider when making recommendations to their patients and the public about PSA testing. The new study still does not answer the question that many are asking – whether screening for prostate cancer actually saves lives – but it does provide more evidence for how often the PSA test should be done. And, the NCI study has generated more points for discussion between men and their doctors about the frequency of screening for prostate cancer.