Michael Gliksman: Screening disparity

THE American College of Physicians released a “guidance statement” earlier this year recommending against prostate cancer screening. Considered in isolation, the reasons seem compelling.

In the US in 2012, more than 241 000 men were diagnosed with prostate cancer and 28 000 died of it. Prostate cancer  is the second leading cause of cancer-related deaths in US men; one in six men (16.7%) will receive a diagnosis of prostate cancer in their lifetime, and 10- and 15-year relative survival rates are 98% and 91%, respectively, although the 5-year survival rate for invasive prostate cancer can be as low as 28%.

In Australia in 2012, prostate cancer was the most commonly diagnosed cancer in men, with a one in eight risk of being diagnosed with it before the age of 75 years. In 2010, 3235 men died from prostate cancer.

The proportion of men who are diagnosed with prostate cancer but never have associated clinical symptoms is difficult to estimate, but it may range from a low of 23% to a high of 66%.

A false-positive rate of 10%–12% for screening prostate-specific antigen (PSA) levels greater than 4.0 ng/mL (and even higher in some studies) and the harms associated with treating men with cancer that would not have become clinically evident in their lifetime have apparently influenced the guidelines to recommend against screening.

But how does this compare with breast cancer statistics and the response to them?

In the US in 2012, about 227 000 new cases of breast cancer were diagnosed in women, with about 40 000 deaths. Breast cancer is the second leading cause of death in women. One in eight US women (12.4%) will receive a diagnosis of invasive breast cancer in their lifetime and 10- and 15-year relative survival rates are 82% and 77%, respectively.

In Australia, breast cancer is the most commonly diagnosed cancer in women, with a one in 11 chance of being diagnosed before age 75 years. In 2010, 2840 women died from breast cancer.

The false-positive rate of 8%–21% for screening mammography and the estimated 10 breast cancers diagnosed and unnecessarily treated per life saved do not seem to have caused the same circumspection as with prostate cancer screening — even though the Cochrane Collaboration concluded it is not clear whether mammography screening does more harm than good.

I have written previously on the conflicting evidence of prostate cancer mortality reduction from screening derived from several studies.

Last year, the PIVOT Study, which assessed treatment by randomly assigning men with local prostate cancer to either radical prostatectomy or observation, found a 13.2% reduction in all-cause mortality among men with a PSA value greater than 10 ng/mL who had a radical prostatectomy. Perhaps if screening was more widely available more men found to have prostate cancer would be able to consider this option.

There is little evidence-based medicine to distinguish efficacy and harms between breast and prostate cancer screening. Yet none of this appears to have influenced some breast cancer screening advocates’ negative attitudes towards screening for prostate cancer.

When there is little to distinguish breast cancer from prostate cancer screening other than gender, men are entitled to ask why there is a difference in attitude and — more importantly — a difference in funding for the two cancers.

Dr Michael Gliksman is an occupational physician based in Sydney and chairman of the Professional Issues Committee of the AMA NSW. On Twitter @MGliksmanMDPhD