A two-tiered system of surveillance could reduce prostate cancer deaths by half while also curbing overdiagnosis and overtreatment, according to results from a large Swedish study.
The system would allow men who test for high levels of prostate-specific antigen (more than 1.6 ng/mL) in their 40s to undergo close surveillance as they age, while the rest – approximately half of all men – would need to be tested only three times between the ages of 44 and 60 years.
The findings, released May 18 and highlighted during a press briefing at which the American Society of Clinical Oncology offered a preview of studies to be presented at its annual meeting in June, could help lead to a more "rational" screening strategy, according to the study’s investigators.
While there is evidence that PSA screening can detect prostate cancer at an early, curable stage, it is viewed as problematic because of the risk of overtreatment. PSA levels are not necessarily indicative of present cancer, and a large number of men must be screened to prevent a single death.
The investigators, led by Dr. Hans Lilja of Memorial Sloan-Kettering Cancer Center in New York, conducted a case-control study nested within a cohort of 12,090 Swedish men who provided blood between 1974 and 1986. A total of 4,999 provided repeat samples 6 years later. The investigators also looked at an independent cohort of 1,167 men who provided blood at age 60 years. Men with evidence of prostate cancer metastasis or death (n = 252) were matched 3:1 with controls.
The study found that 44% of prostate cancer deaths occurred in men who had the top 10% of PSA levels (greater than 1.6 ng/mL) for their age group when they were tested for the first time between the ages of 44 and 50 years.
Men whose PSA levels remained below the median for the population in their age group saw a progressively declining rate of death or metastasis.
The investigators found that 28% of metastases or deaths from prostate cancer over the next 27 years occurred in men aged 44-50 years whose initial screens showed a PSA below the median in the population (0.7 ng/mL).
For men aged 51-55 years with a PSA lower than the median (0.8 ng/mL), the risk of metastatic prostate cancer or death was 18% over 27 years. At age 60 years, only 0.5% of deaths or metastases occurred in men with a PSA less than the median for that age (1.1 ng/mL).
The findings show that PSA levels at the time of initial screening among men aged 44-50 years can accurately predict the risk of death from prostate cancer or metastatic prostate cancer up to 30 years later. Concentrating surveillance in this group of men could allow the rest to undergo only three lifetime tests at the ages of 44, 51-55, and 60 years, the investigators concluded.
Dr. Lilja disclosed owning stock in Arctic Partners, a firm that holds patents for PSA assays.