Wider screening and earlier detection of cancer leads to better patient outcomes.
That?s been the cancer diagnosis dogma for quite a while, and its wisdom has saved many, many lives. It?s therefore somewhat startling to see a high-level medical task force recommend against a widely used cancer detection and screening protocol. But that?s just what happened a few months ago when the U.S. Preventive Services Task Force (USPSTF) updated its recommendation statement regarding prostate-specific antigen (PSA)-based screening for prostate cancer.
Granted, prostate cancer is a somewhat odd medical issue in many contexts. It afflicts vast numbers of men at some time in their lives?some estimates say as many as one in six?and the National Cancer Institute estimates that 28,170 men will die from it in 2012. Yet for many men it?s not an aggressive disease and may even remain asymptomatic. Age is the biggest risk factor, and incidence ramps up steeply with each passing decade. Ethnicity also plays a role, with Asian men possessing the lowest risk and African-American men the highest. And, predictably, a family history of prostate cancer increases risk.
The relatively benign nature of most prostate cancers is one of the reasons PSA screening is now discouraged. Simply living with prostate cancer can be a reasonable course of action, especially among the elderly, but high PSA numbers often lead to overtreatment. Another factor is that the primary intervention, prostatectomy, is a very invasive (a useful euphemism for quite awful) procedure, with a high incidence of side effects such as incontinence and erectile dysfunction. It?s difficult to know for sure, but the expert thinking now is that life with prostate cancer would be of higher quality than life post-prostatectomy for many men.
The issue is still controversial and definitely has my attention. I am early in my ?PSA testing years,? so to speak, and have prostate cancer in my family history, which ups the ante. So I started wondering, what would be a better cancer screen than PSA levels and the infamous digital exam? Or how about at least refining diagnoses if PSA or morphology dictate further inquiry? Maybe we can start genotyping prostate tumors and distinguish those more likely to spread and do harm (the fatality numbers are concerning, no doubt) from those likely to keep to themselves?
Here I ran into some disappointment. There are many papers that say various things about the genetics of prostate cancer, but the overall picture is summarized rather nicely in the NCI?s online ?Genetics of Prostate Cancer? page linked above, last updated less than two weeks ago. ?A better understanding is needed of the genetic and biologic mechanisms that determine why some prostate carcinomas remain clinically silent, while others cause serious, even life-threatening illness.?
Right now the best clue for the hereditary disease involves mutations in the HOXB13 gene, a discovery made early this year. Hopefully this will yield insight into initiation mechanisms and help start making sense of the stew of genes implicated in early prostate cancer genome characterization efforts.
Imperfect though the measurement may be, I will probably get at least a baseline PSA measurement in the next couple of years. If the number should then spike and/or a growth be detected, I?ll at least know that there?s a lower chance of a false positive. But what should I?and men like me?do then? The main problem with PSA isn?t with the measurement itself, but with the subsequent overtreatment. With the current level of understanding, we simply don?t know enough to decide the "correct" course of action. It is only through greater knowledge of cancer genomics that we will be able achieve clarity and make a sound, rational decision to either eradicate a potentially deadly cancer and accept the treatment side effects or learn to live with a growth.
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