Influence of blood prostate specific antigen levels at age 60 on benefits and harms of prostate cancer screening: population based cohort study

OBJECTIVE To determine the relative risks of prostate cancer incidence, metastasis, and mortality associated with screening by serum prostate specific antigen (PSA) levels at age 60. DESIGN Population based cohort study. SETTING General male population of Sweden taking part in a screening trial in Gothenburg or participating in a cardiovascular study, the Malmö Preventive Project. PARTICIPANTS The screened group consisted of 1756 men aged 57.5-62.5 participating in the screening arm of the Gothenburg randomized prostate cancer screening trial since 1995. The unscreened group consisted of 1162 men, born in 1921, participating in the Malmö Preventive Project, with PSA levels measured retrospectively in stored blood samples from 1981. INTERVENTION PSA screening versus no screening. MAIN OUTCOME MEASURES Incidence rate ratios for the effect of screening on prostate cancer diagnosis, metastasis, and death by PSA levels at age 60. RESULTS The distribution of PSA levels was similar between the two cohorts. Differences in benefits by baseline PSA levels were large. Among men with baseline levels measured, 71.7% (1646/2295) had a PSA level <2 ng/mL. For men aged 60 with PSA level <2 ng/mL, there was an increase in incidence of 767 cases per 10,000 without a decrease in prostate cancer mortality. For men with PSA levels ≥ 2 ng/mL, the reduction in cancer mortality was large, with only 23 men needing to be screened and six diagnosed to avoid one prostate cancer death by 15 years. CONCLUSIONS The ratio of benefits to harms of PSA screening varies noticeably with blood PSA levels at age 60. For men with a PSA level <1 ng/mL at age 60, no further screening is recommended. Continuing to screen men with PSA levels >2 ng/mL at age 60 is beneficial, with the number needed to screen and treat being extremely favourable. Screening men with a PSA level of 1-2 ng/mL is an individual decision to be based on a discussion between patient and doctor.