Metastatic disease reduced in PSA screening era, study indicates

Prostate-specific antigen (PSA) screening reduced the number of men presenting with metastatic prostate cancer, a new study found.

Researchers used data from the Surveillance, Epidemiology and End Results (SEER) registry to calculate the incidence of metastatic prostate cancer in 2008 and compared it to annual incidence rates from the early 1980s, before PSA screening was performed. They calculated how many cases of metastatic disease would be expected in the registry population in 2008 based on the 1980s data and came up with 2,277. However, according to the SEER data, only 739 cases were actually observed in 2008, an expected-to-observed ratio of 3.1.

Extrapolated to the total U.S. population, these calculations indicate that about 25,000 men would have been expected to present with metastatic prostate cancer in 2008, compared to the approximately 8,000 that actually did. The researchers concluded that these findings show an apparent benefit to PSA screening. They also found that the benefit increased with age until age 85. The study was published online by Cancer on July 30.

Although the study controlled for age and race, there is still a risk of residual confounding, even by some currently unknown risk factor, the authors cautioned. A second limitation is the issue of lead-time effects. PSA screening could potentially change the age at which a patient presents with metastatic cancer without changing the length of his symptom-free or overall survival. The current study also did not consider the risks of overdiagnosis and overtreatment, the authors noted.

The study was not able to assess the optimal ages to start and stop screening, but the authors concluded that the data showed a significant decline in metastatic cancer attributable to PSA screening. “We believe that these estimates must be taken into consideration (bearing in mind the limitations of observational data) when public health policy-level recommendations are made regarding PSA screening,” they concluded.