Last week, I posted the first half of a talk on cancer medicine I gave at Stevens on February 12. Here is the second half. You can also find the full text on my Scientific American blog “Cross-check.” —John Horgan, Director, Center for Science Writings.
OVERDIAGNOSIS AND OVERTREATMENT
The cancer industry has convinced the public that screening for cancer is beneficial. The earlier we can detect cancerous cells, the more likely it is that treatment will succeed. Right? Wrong. One of the most significant findings of the past decade is that many people have cancerous or pre-cancerous cells that, if left untreated, would never have compromised their health. Autopsies have revealed that many people who die of unrelated causes harbor cancerous tissue.
Tests cannot reliably distinguish between harmful and harmless cancers. As a result, widespread testing has led to widespread overdiagnosis, the flagging of non-harmful cancerous cells. Overdiagnosis leads in turn to unnecessary chemotherapy, radiation, and surgery. Mammograms and prostate-specific antigen (PSA) tests have led to especially high rates of overdiagnosis and overtreatment.
A 2013 meta-analysis by the Cochrane Collaboration, an international association of experts that assesses medical procedures, estimated that if 2,000 women have mammograms over a period of 10 years, one woman’s life will be saved by a positive diagnosis. Meanwhile 10 healthy women will be treated unnecessarily, and more than 200 “will experience important psychological distress including anxiety and uncertainty for years because of false positive findings.”
Another nonprofit medical group, theNNT.com, has spelled out a disturbing implication of these data. The NNT notes that some overdiagnosed women might “die due to aggressive therapies such as chemotherapy and major surgery.” Thus any benefit from screening “is balanced out by mortal harms from overdiagnosis and false-positives.”
As for PSA tests, a federal task force of medical experts estimates that 1.3 deaths may be averted for every 1,000 men between the ages of 55 and 69 tested for 13 years. But for every man whose life is extended, many more will experience “false-positive results that require additional testing and possible prostate biopsy; overdiagnosis and overtreatment; and treatment complications, such as incontinence and erectile dysfunction.” The discoverer of the prostate-specific antigen, pathologist Richard Ablin, has called the PSA test a “profit-driven public health disaster.”
ALL-CAUSE VERSUS SPECIFIC MORTALITY
Studies of tests for a specific cancer generally look at mortality attributed to that cancer. Mammograms are thus deemed effective if women who get mammograms die less often from breast cancer than women who do not get mammograms. This method can overstate the benefits of tests, because it omits deaths resulting, directly or indirectly, from the diagnosis. After all, surgery, chemotherapy, and radiation can have devastating iatrogenic effects, including heart disease, opportunistic infections, other forms of cancer, and suicide.
Therefore some studies measure “all-cause” mortality, death from any cause. A 2015 meta-analysis by epidemiologist John Ioannidis (renowned for bringing the scientific replication crisis to light) and others found no reductions in all-cause mortality from tests for cancer of the breast, prostate, colon, lung, cervix, mouth, or ovaries for asymptomatic patients.
In a recent editorial, Ioannidis and four co-authors argue that cancer screening (especially mammograms and PSA tests) does more harm than good and should be abandoned. They warn that this proposal will be met with “fierce opposition.” Screening, they note, “is big business: more screening means more patients, more clinical revenue to diagnostic and clinical departments, and more survivors in need of care and follow‐up.”
Cancer boosters commonly point to improvements in survival rates, the length of time between diagnosis and death. Survival rates for some cancers have indeed grown as a result of more widespread and higher-resolution testing, which detects cancer earlier. But as a 2015 analysis points out, in general people do not live longer as a result of early detection. They simply live longer with a diagnosis of cancer, with all its harmful emotional, economic, and physiological consequences.
The aggressive, can-do American approach to health care isn’t working when it comes to medicine in general and cancer medicine in particular. Europe, which spends much less on cancer care than the U.S., has lower cancer mortality rates, according to a 2015 study. So do countries such as Mexico, Italy, and Brazil, according to Our World in Data.
The profit motive compromises American cancer care. According to a 2019 essay in Stat News by oncologist Vinay Prasad, many cancer specialists accept payments from firms whose drugs they prescribe. This practice, Prasad agues, “leads us to celebrate marginal drugs as if they were game-changers. It leads experts to ignore or downplay flaws and deficits in cancer clinical trials. It keeps doctors silent about the crushing price of cancer medicines.”
Last year, The New York Times and ProPublica reported that top officials at Sloan Kettering Cancer Center “repeatedly violated policies on financial conflicts of interest, fostering a culture in which profits appeared to take precedence over research and patient care.” Sloan Kettering’s chief medical officer, Jose Baselga, “failed to disclose millions of dollars in payments from drug and health care companies in dozens of articles in medical journals.”
GENTLE CANCER MEDICINE?
Some health-care experts espouse “conservative medicine” as a way to reduce health-care costs and improve outcomes. Conservative cancer medicine, as I understand it, would engage in less testing, treatment, fearmongering, military-style rhetoric, and hype. It would recognize the limits of medicine, and it would honor the Hippocratic oath: First, do no harm.
Physicians cannot bring about a shift toward conservative cancer medicine on their own. We consumers must help them. We must recognize the limits of medicine and the healing capacities of our own bodies. We must resist tests and treatments that have marginal benefits, at best. We may never cure cancer, which stems from the collision of our complex biology with entropy, the tendency of all systems toward disorder. But if we can curtail our fear and greed, our cancer care will surely improve.
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