Just in time for Prostate Cancer Awareness Week (September 19-25, 2010) the British Medical Journal has stepped into the considerable fray regarding using prostate specific antigen (PSA) to screen men for prostate cancer. What pluck! Before discussing these two huge studies, let's first define the issue.
Some years ago, men who developed prostate cancer would be diagnosed at an advanced stage, when treatment amounted to palliation at best. Then along came the observation that much of the time, as prostate cancer develops the antigen PSA is dumped into the blood and can be easily detected. Years of testing, measuring and correlating later, we now have PSA used to screen men for the disease. But we've also noted that higher PSA levels can also be seen in that very common consequence of aging, benign prostatic hyperplasia or BPH. (Loving the acronyms yet?). So rising or high PSAs may or may not signal cancer of the prostate.
Much effort and research has gone into better ways to use the marker, such as measuring its rate of increase rather than an absolute value, limiting screening to men younger than 75, and other strategies. But the fact remains that finding a true marker of prostate cancer rather than simply an antigen produced by the prostate gland all the time, albeit at variable levels, would be infinitely preferable.
What has all this screening given us? Critics would say massive overtreatment of the disease, since along with its other charming attributes, most cancers of the prostate are slow growing and unlikely to kill a man before something else does. And overtreatment can come with unpleasant and expensive consequences, such as urinary incontinence and erectile dysfunction.
Enter our two studies for this week: Screening for prostate cancer, and PSA levels at age 60 and death or metastasis from prostate cancer. The first study was a meta-analysis of almost 400,000 patients and reached the sobering conclusion that PSA screening did not reduce deaths due to prostate cancer or overall mortality. The second study is a great use of blood samples collected from almost 1200 men for another purpose. The men were age 60 at the time of collection, and were followed to age 85. Retrospective measurement of PSA in these samples revealed that when men had a PSA value of 1 ng/ml or less at age 60, their risk of dying from prostate cancer was 0.2% or less. The authors conclude that this finding supports measuring PSA at age 60, then not rescreening men whose levels were 1 or less, effectively eliminating a huge pool of men who may otherwise be overdiagnosed and overtreated. Roar!
Rick and I share the opinion in this week's podcast that any way to decrease the substantial overdiagnosis and overtreatment issues with regard to prostate cancer will help everyone. In previous podcasts Rick has stated that he hasn't been tested and is unlikely to do so. It's worth reminding all concerned that a careful look at each man's risk, including family history and other factors, should be weighed before PSA testing is done.
Other studies this week include factors that may predict who may experience sudden worsening or exacerbation of chronic obstructive pulmonary disease (COPD) in NEJM, and in the same issue, the effect of public smoking bans on hospitalization due to chronic asthma in children Finally, we also talk about best strategies to avoid blood clotting in people at risk but without causing an increased risk of internal bleeding, especially in the gastrointestinal tract in this issue of Archives of Internal Medicine. Until next week, y'all well.