David Ropeik
David Ropeik is a retired instructor of risk communication at Harvard School of Public Health, Boston, and author of Curing Cancer-phobia: How Risk, Fear, and Worry Mislead Us. DRopeik.com
David Ropeik is a retired instructor of risk communication at Harvard School of Public Health, Boston, and author of Curing Cancer-phobia: How Risk, Fear, and Worry Mislead Us. DRopeik.com
Colonoscopies…mammograms…PSA tests…lung cancer screenings—sometimes it seems that every doctor appointment includes a recommendation for some sort of cancer screening. Few patients question this—getting screened for cancer seems the best way to reduce the risk posed by the world’s most feared disease.
But is cancer screening as beneficial as we think it is? In 2023, researchers at Norway’s University of Oslo conducted a review of 18 earlier long-term clinical trials of common cancer screenings. Their surprising conclusion: With the potential exceptions of colorectal cancer screenings, the evidence does not show that these screenings extend lives.
This Norwegian study is controversial—researchers based their conclusion on how cancer screening affected overall death rates, not just the odds of dying from cancer. But this was not the first study to cast doubt on cancer screenings. Example: Numerous large-scale studies examining decades of data from the US, Denmark, Australia and other countries have found that routine mammograms do not significantly reduce cancer deaths.
This doesn’t mean that patients should reject doctors’ cancer-screening recommendations. But it does mean that you should know some key details before proceeding…
Routine cancer screenings have a recommended starting age. Example: When you hit 50, your doctor probably told you it was time to start getting colonoscopies…in recent years, that starting age has been dropped to 45.
There’s also an age above which routine screenings no longer make sense—colonoscopies generally should stop at age 75…lung cancer screenings at 80…PSA tests for prostate cancer at 70…and cervical cancer screenings at 65, based on recommendations from the nonprofit US Preventive Services Task Force (USPSTF).
It isn’t that people don’t get cancer above these ages, but once people pass these ages, it’s increasingly unlikely that a cancer that does develop will kill them. They likely will die from something else first, including heart disease, stroke, infections…even falls. Certain cancers, such as breast and prostate cancers, tend to progress more slowly in older patients. Yet many people continue getting cancer screenings long after they pass the recommended stopping-point ages—patients don’t like hearing that they’re too old for cancer screening, and their doctors don’t like explaining this.
Some researchers argue that a degree of flexibility is warranted with cancer screenings end dates. Example: If a 75-year-old is in excellent health and has a family history of longevity, perhaps he/she has a sufficient expected lifespan that it’s prudent to continue screening for colon cancer a while longer. But it’s also worth balancing this against the risks inherent with the colonoscopy itself, which include perforated colon, gastrointestinal bleeding and cardiovascular complications. The risks are statistically worthwhile for people younger than 75, but the odds that a colonoscopy will cause complications, adverse effects or death are significantly higher for elderly patients, according to a study by a researcher at University of Washington School of Medicine.
Treating cancer before it spreads can dramatically increase survival rates…and screening regularly spots cancers that haven’t yet spread. So why does the data not provide more clear-cut proof that cancer screening extends lives?
The answer might lie in a problem known as overdiagnosis. Screenings often find cancers that are never going to progress or will progress so slowly they are never going to cause issues during the patient’s lifetime even if untreated. Examples: 50% to 60% of prostate cancers detected by PSA tests and 50% of lung cancers detected by chest radiography or sputum exam fall into these not-dangerous categories, according to a 2019 paper by researchers at the National Cancer Institute and other organizations. Studies that found mammograms don’t significantly reduce cancer deaths inevitably also find that mammograms do lead to the discovery of not-dangerous breast cancers.
The fact that cancer screening might spot a non-troublesome cancer doesn’t mean we shouldn’t screen for cancer—the screens also could find potentially lethal cancers. But it does create a significant risk that patients will receive life-changing and potentially dangerous treatments for non-dangerous cancers.
Patients who are told that a test detected cancer need to remain calm enough to choose a course of treatment appropriate for their cancer. Sometimes the best option will be to do nothing other than monitor the cancer. But that can be very difficult when confronted with a cancer diagnosis, because of our action bias—the psychological tendency to want to do something rather than nothing, even when nothing is probably the best option.
So the question is, Who can we trust to tell us whether a cancer screening test has real value? It isn’t easy to find an unbiased opinion. After all, medical practices and health-care companies make money when we have tests done. And most doctors default to having tests done even when it’s not clear that those tests are useful—medical professionals also fall victim to action bias. Cancer patient advocacy nonprofits often heavily promote screening—but many of these organizations receive substantial funding from pharmaceutical and medical-products companies, raising questions about their objectivity.
One organization that provides objective guidance about medical tests is the USPSTF. You can find out what this nonprofit says about a cancer screening before having it done. (On US PreventiveServicesTaskForce.org, choose “Published Recommendations” from the “Recommendations” menu, then select “Cancer” from among the search options.) The USPSTF assigns letter grades that summarize how highly it recommends a test. These grades are based on wide-ranging research that looks at how many lives the screening saves…at what intervals and for which ages…and what harms the screening causes, such as false-positives and false-negatives or overtreatment of conditions that frighten but don’t clinically require aggressive treatment. The recommendations also clearly state the degree of confidence the expert panel has in the evidence. Lower ratings will say things like “modest confidence that….” Examples: Cervical cancer screening receives an A for women ages 21 to 65, but a D for women outside that age range…PSA tests for prostate cancer receive an unimpressive C for men ages 55 to 69 and a D for age 70 and up…colorectal cancer screening receives an A for ages 50 to 75, but a B for people in their late 40s and a C for people ages 76 to 85. Ovarian cancer and thyroid cancer screenings earn Ds—they are not recommended for asymptomatic patients at any age.
Stats and studies can suggest how valuable a particular cancer screening is for the average person of your age—but you might not be an average person. If one of your parents, grandparents or siblings died of cancer, there’s a good chance that the value of a test that screens for that cancer is significantly greater for you than for the average person. If you smoke, drink heavily or are obese, cancer screenings might have greater value to you as well. Certain ethnic groups are at elevated risk for specific cancers, potentially increasing the value of screening. Examples: Black men are at elevated risk for prostate cancer…Ashkenazi Jewish women are at elevated risk for breast cancer.
