Ben Stiller, 51, the American actor, comedian, and filmmaker, recently revealed that he had been diagnosed with prostate cancer in June 2014, and following surgery had been informed that he was free of cancer.
Stiller has said that he believes that PSA testing saved his life by detecting his prostate cancer “early enough to treat.” Based on the best evidence available, however, it seems unlikely that Ben Stiller’s life was saved by PSA screening. In fact, he would probably be fine whether he was screened or not. Meaning he would have been diagnosed with prostate cancer at a time in the future when he experienced clinical symptoms of the disease like urinary retention, hesitancy or urgency; received treatment and had a good outcome.
But evidence pales in comparison to belief; and belief in the narrative of “prevention” generally and “early detection of cancer” specifically is strong and consistent with age-old, cultural idioms like “an ounce of prevention is worth a pound a cure.”
Mr. Stiller writes, “But without this PSA test itself, or any screening procedures at all, how are doctors going to detect asymptomatic cases like mine, before the cancer has spread and metastasized throughout one’s body rendering it incurable?” However, the only way to know if screening is effective for any particular cancer is to subject it to randomized controlled trials. In the case of prostate cancer screening, trials have been done with hundreds of thousands of patients across the world and prostate cancer screening has not been demonstrated to be efficacious.
So what’s all the controversy about?
De-adoption of entrenched medical practices is hard.
Cognitive dissonance surely plays an important role. Physicians want to do good for their patients and the sincere belief in this mission is closely tied to many physicians’ self-esteem. I haven’t met one yet who bragged about the score of men rendered impotent by their actions – all for nothing! That’s a tough pill to swallow. It’s much easier to shoot the messenger, deny the accumulating evidence or quibble over technicalities.
Then there are financial motives. Cancer screening is big business. The direct revenue generated from screening tests and the downstream revenue generated by positive results is massive. A recent study in JAMA Internal Medicine reported that following the United States Preventive Service Task Force (USPSTF) recommendation against PSA screening, primary care physicians reduced PSA testing by 57% compared to only 4% for urologists.
Misattribution bias contributes as well. The clinical observation of a high success rate for treating cancer detected by screening facilitates the mistaken belief that the screening is responsible for success despite the fact that the cancer would have responded to treatment regardless if it has been detected later. And the clinical observation of a lower success rate for treating metastatic cancers not detected by screening facilitates belief that screening and detection at an earlier stage could have prevented a bad outcome when in reality they couldn’t.
In the end we’re only human. We are risk adverse creatures, inclined to believe we control our own fate to a much larger extent than is probably true. Cancer screening, along with many other health services categorized as preventative, satisfies our need to feel like we are doing all that is objectively possible to prevent suffering and death. But in the case of PSA screening, it doesn’t. In fact, the best evidence tells us it does more harm than good.
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