The European Randomised Study for Prostate Cancer (ERSPC), conducted in seven countries, showed a 31 percent reduction in cancer mortality in men who underwent routine screening. Now, results from a Swedish trial that is part of the larger ERSPC study suggest that PSA screening for prostate cancer may substantially improve cancer-specific survival.
After 14 years of follow-up, the study, a subgroup of the larger ERSPC trial, conducted in Sweden showed an approximate 50-percent reduction in prostate cancer mortality among men age 50 to 64 (at the time of study entry) who were offered routine PSA screening compared with men not offered routine screening. The results published recently in Lancet Oncology confirm that the numbers needed to screen and treat to prevent one prostate cancer death were much smaller than reported in the ERSPC study: only 293 men where screened and 12 diagnosed or treated to prevent one death from prostate cancer.
The improved results are most likely related to longer follow-up (14 years compared with 11 years) and that the median age of the men in the Swedish trial was also more than 4 years younger (56 compared with over age 60), which is important because younger men are likely to benefit more from early diagnosis than older men.
Furthermore, very few men in the Swedish trial had ever had a PSA screening test before enrolling in the study, including men in the control arm, meaning there was very little contamination. This is an important difference compared with the American PLCO trial, in which 40 percent of participants had already been screened with a PSA test at study entry.
During the course of the trial, the state of prostate cancer screening in Sweden was very different from the situation in the United States now where testing is ubiquitous in the community, making it extremely difficult to avoid contamination in the “non – screened” arm of any randomised trial. The Swedish cohort provided the longest follow-up and the highest mortality benefit from PSA screening in the ERSPC trial.
There is increasing data suggesting that a baseline PSA in men in their 40s and subsequent PSA velocity (the rate of increase in PSA levels) can predict both lifetime risk of developing cancer and of potentially lethal cancers. Such an approach could help identify men at high risk who may benefit from chemoprevention or men diagnosed with biologically significant cancer who would benefit from early intervention.
The substantial mortality reduction in the Swedish study was achieved despite men in both arms diagnosed with low- to moderate-risk disease receiving comparable treatments and with a significant portion of the men in the screening arm undergoing active surveillance that is, they chose to forgo definitive treatment, such as surgery or radiation, until there was evidence of progression. More than one-quarter of those men are still under an active surveillance regimen.
In conclusion, this new data clearly shows a benefit to screening in men less than 70 years of age.