November 8th, 2011

Putting Prostate Screening Controversies in Context

By msequeira

Men and their doctors should pursue a “shared decision-making process” about prostate cancer screening, advises Richard M. Hoffman, MD, MPH, in a recent paper published in the New England Journal of Medicine. Dr. Hoffman, a Professor of Internal Medicine at the University of New Mexico and member of the UNM Cancer Center who practices at the New Mexico VA Hospital, provides timely guidance for physicians and patients wrestling with the complexities surrounding prostate-specific antigen (PSA) testing, the screening method that has been widespread since the late 1980s yet is currently at the center of controversy.

That controversy deepened last month when the US Preventive Services Task Force issued its draft recommendation (now under public comment) against PSA screening for men without prostate-related symptoms. The committee pointed to the lack of evidence that PSA testing improves overall survival and highlighted the harms of overdiagnosis – the diagnosis of cancers that will never cause symptoms or death during the patient’s lifetime. Overdiagnosis is a “hidden downside” of prostate cancer screening for two primary reasons: it can lead to invasive treatments that carry the risk of complications, including urinary, sexual and bowel dysfunction; and it can cause considerable mental anguish in men who, regardless of their treatment decision, “know they have cancer.”

Dr. Hoffman’s paper carefully sifts the available evidence for and against PSA screening, and advocates an approach to screening decisions that involves educating patients about their personal cancer risk, the slow-growing nature of many prostate cancers, the often limited accuracy of screening and diagnostic tests and the benefits and harms of screening.

While cancer screening is often promoted as an unmitigated good, the reality is a bit more complicated. In the case of prostate cancer, the introduction of PSA testing has nearly doubled the number of prostate cancer diagnoses – by detecting cancers an estimated five to 10 years before they would otherwise be discovered – yet the test has not been shown to improve men’s overall survival. How to account for this seeming paradox? Most prostate cancers are slow-growing and the “great majority of men with a diagnosis of prostate cancer die from other causes,” explains Dr. Hoffman. However, existing screening and risk-assessment methods cannot perfectly predict which cancers are potentially lethal and which are not. As a result, many men diagnosed with early-stage cancer opt for some form of treatment, and inevitably some of those men will be treated – and perhaps harmed by treatment complications – for cancers that would never have posed a health risk.

One alternative, Dr. Hoffman points out, is the increasingly used approach of “active surveillance,” in which patients with abnormal PSA values are carefully monitored, through a combination of regular PSA testing and biopsy, rather than immediately treated. Such approaches are currently being tested against treatment of early-stage cancers to see whether there is a survival benefit for men either way.

Other alternatives to blanket treatment rely on the eventual identification of biomarkers for aggressive forms of prostate cancer, an area of intensive research. Such markers would allow physicians to distinguish threatening cancers from relatively non-threatening ones and use that information to guide treatment decisions.

In his paper, Dr. Hoffman examines the results of two recently reported randomized trials, a European study known as ERSPC and a US study known as PLCO. The European study, conducted at seven centers, randomly assigned 182,160 men aged 50 to 74 years to regular PSA screening (every four or every two years) and to no screening. The US study randomly assigned 76,693 men, between the ages of 55 and 74 years, to annual PSA testing for six years and annual digital rectal exam for four years or to no screening. The ERSPC trial showed a small survival benefit among men who received screening (primarily driven by the results of one of the seven study centers), while the PLCO trial did not show any benefit.

Dr. Hoffman emphasizes that these results – which are still undergoing scrutiny and debate – do not invalidate PSA testing. Regular PSA tests may be critical for men at greater-than-average risk of developing prostate cancer, particularly men in two known high-risk groups: African American men, who have the highest incidence of prostate cancer in the US; and men with a first-degree relative with a prostate cancer diagnosis.

For men of normal risk, screening decisions should be made between each patient and his physician based on a “shared decision-making process that elicits [the patient’s] values and preferences for the potential consequences of testing,” writes Dr. Hoffman. He advocates the use of “decision aids,” including video, written and web-based materials, to inform patients of the risks and benefits of screening. That information, together with open conversations between men and their doctors, will help men make the best decisions – about screening as well as treatment – for their own individual situations.

Prostate cancer is the most frequently diagnosed cancer in men, excluding skin cancer, and second only to lung cancer as a cause of cancer death. Approximately 240,000 American men will be diagnosed with prostate cancer this year, and 34,000 men will die of the disease.

Tags: Press Release Archive 2011, Prostate Cancer, publication, Screening/Prevention Prostate Cancer