Diagnostics & Imaging Week

Sometimes a cure can have effects worse than the disease – and have faster, even deadlier, effect.

A prominent case in point: Men 75 or older should not be screened for prostate cancer, according to the U.S. Preventative Services Task Force (USPSTF), because there is evidence of more harm than benefit from carrying out this procedure and providing therapy based on a positive diagnosis.

The task force made this recommendation early this week, saying it is based on evidence that the benefits of prostate cancer treatment are "small to none" in older men.

Also, the group found that treatment based on routine screening causes "moderate-to-substantial" harm to men of all ages, such as erectile dysfunction, urinary incontinence, bowl dysfunction, and death. These harms are especially important, the task force notes, because some men who are treated for prostate cancer would never have developed symptoms during their lifetime.

Even the screening process itself can cause pain and discomfort, such as those associated with prostate biopsy and the psychological effects of false positive results, the task force said.

For men younger than 75, the issue falls into a very grey area, it said. The task force said that for this age group, there is not enough evidence to recommend either for or against prostate cancer screening.

As for detection, the task force did find convincing evidence that prostate-specific antigen (PSA) screening can detect some cases of prostate cancer, which it called the most common non-skin cancer and the second leading cause of cancer death in men in the U.S.

A previous review of the issue – performed for the USPSTF in 2002 – found insufficient evidence that screening for prostate cancer improved health outcomes, including mortality, for men of all ages. However, that review also found little evidence concerning the possible downsides of the screening process or the natural history of prostate cancer cases detected with screening.

The task force also noted that even if prostate cancer screening is effective, the disease usually takes at least 10 years to result in the patient's death. Because a 75-year-old man has an average life expectancy of about 10 years, very few men over 75 would experience a mortality benefit from the screening.

Similarly, younger men with chronic medical problems and a life expectancy of fewer than 10 years are also unlikely to benefit from screening and treatment.

Given the slow growth of this type of cancer, there has been a growing debate in recent years over the management of prostate cancer with many experts recommending the "watchful waiting" approach over interventional strategies.

More recently, there has been considerable debate concerning the accuracy of the PSA test, shown to have a false positive rate of 70%. The USPSTF says, however, that the PSA test is more sensitive than the digital rectal examination for detecting prostate cancer.

The conventional PSA screening cut-point of 4.0 g/L detects many cases of prostate cancer; but some early cases will be missed by this cut-point. Using a lower cut-point to define an abnormal PSA level detects more cases of cancer, the task force said.

Some newer tests are in development to make it easier for men to get screened for prostate cancer.

One example is a new test strip, similar to urine-based pregnancy tests, from Gentag (Washington) and MacroArray Technologies (Philadelphia). The companies have teamed up to design a wireless immunoassay incorporating Gentag's cell phone communication technology and MacroArray's urine diagnostic test for prostate cancer. Gentag CEO John Peters, MD, told Diagnostics & Imaging Week in June that FDA approval of the test is likely still two years away.

Variations of PSA screening, including the use of age-adjusted PSA cut-points, free PSA, PSA density, PSA velocity, PSA slope, and PSA doubling time, have been proposed to improve detection of "clinically important" prostate cancer cases, the USPSTF said. However, no evidence suggests that any of these testing strategies improves health outcomes, the task force noted.

The task force also urged doctors not to order the PSA test for men younger than 75 without first discussing with the patient the potential "but uncertain" benefits and the known harms of prostate cancer screening and treatment.

"Men should be informed of the gaps in the evidence and should be assisted in considering their personal preferences before deciding whether to be tested," the USPSTF said in a statement.

In addition to "watchful waiting," other management strategies for localized prostate cancer include active surveillance (periodic biochemical monitoring with conversion to curative treatment if disease progresses), radical prostatectomy, external-beam radiation therapy, and brachytherapy (or radioactive seed implantation therapy).

According to the task force, about 218,890 U.S. men were diagnosed with prostate cancer last year, and one of every six men in the U.S. will be diagnosed with the disease in his lifetime.

Roughly 27,350 men died of prostate cancer in the U.S. in 2006.