Screening for early cancer detection may reduce the rate of related metastatic disease, but not always.
In a published study in the New England Journal of Medicine, researchers evaluated the incidence of men having a diagnosis of advanced, metastatic prostate cancer at the initial prostate cancer diagnosis. The researchers data from the Surveillance, Epidemiology, and End Results (SEER) Program database. Their analysis included only those men who had been diagnosed with advanced prostate cancer at diagnosis, not of early-stage disease that then progressed to metastasis.
In this perspective study the authors describe trends in metastatic prostate cancer prior to and more than a decade after the widespread use of the prostate-specific antigen (PSA) test. They found that the incidence of initial diagnoses of metastatic prostate cancer fell by approximately 50% within 7 years of the start of the widespread use of PSA tests in 1990.
One of the researchers, Dr Welch said that “the rapid uptake of PSA screening in the United States led to a dramatic spike in overall prostate cancer diagnoses during the early 1990.”
In their discussion of their findings, the study authors postulated that the many interventions we have made to reduce prostate cancer risk as well as the reductions in environmental carcinogens might contribute to a reduction in the incidence of prostate cancer, but they believe that “it’s hard to imagine another factor [other than PSA screening] changing and exerting an effect so quickly.”
Prostate cancer expert Anthony V. D’Amico, MD, PhD, who was not involved with the new essay, agreed with this conclusion. “The initial spike in all prostate cancer incidence following PSA screening was due to the test identifying all the undiagnosed clinically occult disease missed on digital rectal examination……Earlier detection of prostate cancer means that diagnosis of metastatic disease at presentation is less likely to occur.”
D’Amico added that, “Because prostate cancer is generally a slow-growing disease, picking it up early through annual PSA screening would be expected to reduce the occurrence of late-stage [ie, metastatic] disease.”
According to Dr. D’Amico, the recommendation of the United States Preventive Task Force against PSA screening is likely to reverse this trend in the incidence of initial metastatic disease being diagnosed. We should expect to see an increasing number of men initially diagnosed with metastatic, or advanced prostate cancer.
The stark reality of D’Amico’s is best summed up when he said, “We will not see this for another 7 years, but expect death rates to incline in 7 years, given that the survival curves from the European Randomized Study of Screening for Prostate Cancer and Gotenberg where PSA-based screening studies started to separate in favor of PSA screening approximately 7 years following randomization to PSA screening vs usual care.”
N Engl J Med. Published online October 28, 2015.