The secret harms of cancer screening
“Screening saves lives” is a popular sentiment, shared often by cancer advocacy groups, the media, hospitals, and health professionals. It is much less often that these actors point out the potential downsides of cancer screening. In a recent piece in Elemental, physician and journalist Keren Landman explores the hidden harms of cancer screening, highlighting a topic that most clinicians and health care media avoid.
Screening, i.e. testing individuals for a disease or condition before they show symptoms, does reduce cancer deaths for certain cancers in certain populations. For example, cervical cancer screening in women age 21-65 is recommended to find and treat pre-cancerous lesions. Similarly, colon cancer screening for individuals age 50-75 can detect early-stage colorectal cancer and, in many cases, eliminate it.
But not all cancers are detectable through screening, and not all detected cancers are harmful. As Gilbert Welch, a senior researcher in the Center for Surgery and Public Health at Brigham and Women’s Hospital in Boston, explained in a 2019 piece in the New England Journal of Medicine, we are diagnosing certain cancers more, but the mortality rate for these cancers has remained the same.
For example, we are finding many more cases of thyroid cancer and melanoma now than in previous decades. New scanning technology has increased the rate of incidental findings of small harmless thyroid tumors, leading to more “findings” of thyroid cancer. Similarly, increased melanoma screening and new dermatology tools have increased diagnosis of melanoma. However, the rates of metastatic cancer incidence and mortality have remained stable since 1975, indicating that much of these new cases are overdiagnosis.
Some cancers will never grow or cause harm, but it is not always possible for pathologists to distinguish between these harmless cancers and life-threatening cancers–so we treat all cancers aggressively. The result: people are harmed unnecessarily by cascades of further testing and procedures, not to mention financial hardship.
Why don’t more doctors engage patients in a conversation about the harms and benefits before conducting cancer screening? Shared decision making conversations are very challenging, especially because doctors have limited time with patients. Doctors may also be graded or judged based on their screening rates, giving them an incentive to screen more.
Lown Institute senior vice president Shannon Brownlee also pointed out that doctors may be loath to acknowledge the harm they have inadvertently caused through screening. “This is how they’ve defined themselves — ‘I save lives,’” says Brownlee, in Elemental.
“This is how they’ve defined themselves — ‘I save lives.’”Shannon Brownlee, in Elemental.