Healthy men may benefit from screening
Crawford et al conducted a post hoc analysis of the PLCO trial, which had found no benefit to annual PSA testing and serial DRE compared with usual care for the general population.2 Their analysis compared the mortality benefits (both prostate cancer–specific and overall) of annual PSA screening for healthy men with no or minimal comorbidities vs the mortality benefits for men with any risk factor for the 2 leading causes of death: cancer and cardiovascular disease.
Annual PSA testing yielded more diagnoses of prostate cancer in both healthy and at-risk men. Deaths from prostate cancer were infrequent in both groups, occurring in 0.22% (164/73,378) of all participants.
Men with ≥1 risk factor had similar prostate cancer–specific deaths with both yearly screening and usual care (62 vs 42 deaths, adjusted hazard ratio [AHR]=1.43; 95% CI, 0.96-2.11); their prostate cancer–specific mortality rate was 0.27% (95% CI, 0.21-0.34) and 0.19% (95% CI, 0.14-0.25), respectively.
However, healthy men younger than 75 years had fewer prostate cancer–specific deaths with annual PSA screenings (22 vs 38; AHR=0.56; 95% CI, 0.33-0.95; P=.03). Specifically, the prostate cancer mortality rate was 0.17% (95% CI, 0.11-0.25) in the group that received screening vs 0.31% (95% CI, 0.22-0.42) in the usual care group. Thus, the absolute risk reduction for prostate cancer-specific mortality in men without comorbidities who received yearly screening instead of usual care was 0.14% (0.31% vs 0.17%, P=.03), with a number needed to screen of 723 to prevent one death from prostate cancer. There was a non-significant reduction in all-cause mortality in the intervention group vs the control group (AHR=0.93; 95% CI, 0.86-1.02; P=.11).
WHAT’S NEW: At best, screening has a small benefit
These trials indicate that only a small group of men will potentially benefit from PSA screening. Prior to this meta-analysis, a Cochrane review published in 2006 had concluded that there was insufficient evidence to support or refute the routine use of mass screening for prostate can-cer.10 The meta-analysis by Djulbegovic et al, which included 4 additional trials, 2 of them large, found no benefit of PSA screening in reducing mortality from prostate cancer for the general population.1
Annual screening does appear to provide a small reduction in prostate cancer deaths but no significant reduction in all-cause mortality in men younger than age 75 who have no risk factors for cancer or cardiovascular disease.
CAVEATS: Study limitations, some unknowns
These studies did not address whether certain groups at higher risk of developing prostate cancer, such as African American men and those with a family history of prostate cancer, would benefit from PSA screening. In addition, both of the studies detailed in this PURL had substantive weaknesses.
Methodological limitations of the studies in the meta-analysis included the lack of intention-to-treat analysis and allocation concealment, which favors finding a benefit for the screening arm, and PSA screening in the nonscreening arm, which biases the results toward not finding a screening benefit that might exist. Despite these weaknesses, this meta-analysis brings together the best available evidence of the value of screening for prostate cancer.
In addition, there was no quantitative assessment of complication rates included in the meta-analysis. None of the 6 trials collected data on the effect of screening or treatment on participants’ quality of life.
In the post hoc study showing a benefit for screening healthy men, the decrease in prostate cancer deaths was small in magnitude, did not have an impact on all-cause mortality, and was of marginal statistical significance. Although the data came from the largest multicenter study to date of prostate cancer screening, the results of a post hoc analysis of a single trial should be interpreted with caution. The study was initially designed to test the effect of screening on a general population. Whenever a study deviates from the original hypothesis to evaluate a subset of the study population, the investigators increase the risk of finding a difference where none exists. Thus, it is possible that the findings of benefit for healthy men may not truly be present.
What’s more, the risk factors identified by the authors could be interpreted as arbitrary. They included diverticulosis, which is not known to increase the likelihood of cancer or heart disease, as a risk factor. By the same token, smoking—a known risk factor for both cancer and cardiovascular disease—was not addressed. Finally, potential harms associated with false-positive tests and prostate cancer treatment were not addressed in these studies.