Medical Reading

Population-Based Screening Efforts For Prostate Cancer Save Lives

October 10, 2017

Does population-based prostate cancer testing actually save lives and, if so, how many men need to be tested in order to save one life? These questions were addressed by top prostate cancer experts at the 105th Annual Scientific Meeting of the American Urological Association (AUA).

Early Detection of Prostate Cancer (Tyrol Prostate Cancer Demonstration Project 1988-2008)

20 Years Experience: Researchers in Innsbruck, Austria, evaluated data from Tyrol Austria, where an early detection and treatment program has been in place for more than 20 years and found that these programs have been associated with a reduction in mortality in areas where effective treatment is available to all men. The Tyrol project was started in 1988, offering free prostate-specific antigen (PSA) testing to men ages 45-75 years starting in 1993. In men with organ-confined lesions, prostatectomy was recommended (2,153 radical prostatectomies were performed); 86.3 percent of patients with T1 or T2 disease were treated with low-morbidity radical prostatectomy, 8.7 percent with brachytherapy, and 8.7 percent with radiotherapy. After one year, 95.1 percent of men were continent and potency was persevered in 78.9 percent of men younger than 65 years of age. Researchers found that since 1996, a significant reduction in mortality from prostate cancer has been observed in the Tyrol. In the years 2003-2008, prostate cancer mortality rates decreased by 48 percent, 55 percent, 52 percent, 49 percent, 41 percent, and 64 percent (2008) respectively. Researchers concluded that when screening and treatment are available and free, prostate cancer mortality is decreased by population-wide screening efforts.

What is the True Number Needed to Screen and Treat to Save a Life with PSA Screening?

Prostate cancer is a leading cause of cancer deaths in the Western world. One way of decreasing prostate cancer deaths is through screening with prostate-specific antigen (PSA) blood testing. However, the tradeoff between reducing prostate cancer deaths and possible over diagnosis and over treatment is the subject of continuing intense debate. In 2009, prospective, randomized clinical trials of prostate cancer screening reported disparate results, with the Prostate, Lung, Colorectal, Ovarian Cancer (PLCO) trial finding no mortality benefit and the European Randomized Study of Prostate Cancer Screening (ERSPC) showing a 20 percent mortality benefit (30 percent in men actually screened). However, ERSPC estimated that at a median follow-up of 9 years, 1410 men would need to be screened (NNS) and 48 treated (NNT) to avoid 1 prostate cancer death. The most frequently quoted and troubling statistic to physicians and patients alike is the estimate that 48 men need to be treated to prevent 1 PCa death, which is high compared with a NNT of 10 for breast cancer screening. Alternative explanations for a high NNT could be that screening over detects a large proportion of indolent cancers or that the limited follow-up of the ERSPC population overestimated the true NNS and NNT. Using extrapolated data from the ERSPC, a multi-center team of researchers set out to discover the true number of men that needed to be screened (NNS) for prostate cancer and the number needed to treat (NNT) in order to save one life and to assess the effect of follow-up times on these calculations. Based on published ERSPC data, researchers from Chicago and Baltimore estimated the cumulative hazard ratios and NNS/NNT out to 12-years of follow-up. At year 10, the model yielded an NNS of 837 and NNT of 29, similar to the ERSPC report; by year 12, the NNS decreased to 503 and the NNT was 18. The numbers needed to screen and treat to save a life are directly affected by the length of follow-up; thus, we are seeing only the early effects of screening, and more than 10 years of follow-up may be necessary to truly show the value of population-based prostate cancer screening. A prominent feature of prostate cancer screening is that the benefits take a long time to achieve and the true magnitude of over diagnosis and over treatment remain largely unquantified.

"The Tyrol study shows the benefits of freely available PSA testing and the importance of effective treatment once cancer is found," said AUA spokesman Christopher Amling, MD. "Although the ERSPC screening study showed a significant mortality reduction with PSA screening, it also showed that with early follow-up, a relatively large number of men need to be screened (NNS) and treated (NNT) to prevent one prostate cancer death. By extrapolation of data from the ERSPC trial, the researchers from Chicago and Baltimore were able to demonstrate that with longer follow-up the NNS and NNT are significantly lower suggesting that the value of PSA-based screening may be greater than this study suggests."

The AUA believes that early detection of and risk assessment for prostate cancer should be offered to asymptomatic men 40 years of age or older who have a life expectancy of at least 10 years.

American Urological Association