PSA Test Ineffective in Predicting Lethal Prostate Cancer

The prostate-specific antigen (PSA) screening test has been universally accepted as an important tool in the early diagnosis of prostate cancer. However, a troubling new study published in the current issue of the Journal of the National Cancer Institute calls into question its ultimate benefit, concluding that PSA values and their rates of change are “poor predictors of lethal prostate cancer.”

The study, led by Dr. Katja Fall of the Karolinska Institutet in Stockholm, Sweden, and known as the Scandinavian Prostate Cancer Group Study No. 4, focused on 267 Scandinavian men with localized prostate cancer who were diagnosed between 1989 and 1999 and who were managed by watchful waiting. While certain PSA values and rates of change were indeed associated with lethal prostate cancer, the “accuracy of classifying the disease as either indolent or destined to progress was low,” the authors explain.

“We conclude that PSA measurement is associated with prostate cancer prognosis and continues to be an important monitoring tool,” they write. “However, early PSA characteristics perform poorly in distinguishing those who develop a lethal prostate cancer from those at low or no risk of disease progression. Therefore, better decision tools are needed for active monitoring of patients with early disease.”

In an accompanying editorial, Dr. Dipen J. Parekh and cohorts note that, although the PSA test is “largely responsible” for an increase in prostate-cancer diagnosis and detection, it does not necessarily deserve all the credit for the 31 percent fall in prostate-cancer mortality rates between 1990 and 2003. According to Parekh, the results of the study “show the challenges with using PSA measures to identify tumors that meet the ultimate definition of ‘biologic aggressiveness,’ causing the death of the patient.”

“In the ideal circumstances,” the editorial says, “a man on active surveillance for prostate cancer expects that his PSA data will tell his physician one of two things: 1) he has a potentially deadly tumor that must now be treated or 2) he has an indolent tumor that can be safely watched, sparing him the side effects of treatment.” Unfortunately, the PSA test may not be able to accurately determine which category a patient falls into.

“Without becoming despondent and simply treating all men with prostate cancer–accepting the substantial risk of overtreatment and its consequences–how can we better identify the patient with low-risk disease in whom active surveillance is a reasonable option for management?” Parekh asks. “Although PSA level and its kinetics are clearly associated with the behavior of individual prostate cancers,” he acknowledges, “they are not sensitive or specific for the tumor that will ultimately cause harm to a patient.”

According to Parekh, “These data demand that clinical trials commence now to examine surveillance strategies to help patients and their physicians identify and treat tumors that will otherwise be life threatening and to carefully follow those that will not.”

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