Premature detection can lead to an overdiagnosis of cancer, which often causes patients to undergo unnecessary and potentially harmful treatments, according to a study by Dartmouth Medical School professors H. Gilbert Welch and William Black. The study printed online by the Journal of the National Cancer Institute on April 22 also found that overdiagnosis contributes to escalating health care costs and harms patients prescribed invasive and aggressive treatments, according to Welch.
The study is a compilation of "two decades" of work by Welch and Black that has been published amid a larger ongoing debate on the importance of cancer screening tests, Welch said in an interview with The Dartmouth.
Last fall, the U.S. Preventative Service Task Force a committee convened by the U.S. Public Health Service to make assessments of clinical practices and provide recommendations for primary care givers made its policy on mammograms more conservative in order to mitigate overdiagnosis, according to Welch.
"They said for women to get them later in life and less frequently every two years instead of every year," he said.
Cancer screenings are often skewed to yield a greater number of detected abnormal cells, which do not necessarily indicate harmful cancer, according to Welch.
"The worst test is the one that finds the most cancer," he said. "The really important thing is to find the cancers that are going to matter."
Results from the study show that "if we look hard enough, all of us harbor abnormal cells that could lead to cancer," Welch said. Out of trials conducted, approximately 25 to 60 percent of patients would die of other causes before they would ever show symptoms of cancer, or they were diagnosed with cancer that would never progress into a serious form.
"[Overdiagnosis is] just part of the problem that comes with looking hard for early forms of cancer," Welch said. "We get caught in the problem of telling people they have cancer unnecessarily when it isn't going to bother them."
Now that the problem of overdiagnosis has been identified, members of the medical community should begin "the second line of research to study the effect of changing diagnostic thresholds," he said. Welch recommended that cancer screening tests only search for the larger abnormalities that actually grow into harmful forms of cancer.
"A test can be equally as effective at reducing death if we say the only things that need to be followed up on are larger things," Welch said. "The tests we have now can just see such small abnormalities, and that can lead to more harm than good."
Patients who are overdiagnosed with cancer are treated even though they will never show symptoms of the diseases, leading to unnecessary medical expenditures, according to Black.
"It has huge implications for health and the economy," Black said. "If you start diagnosing people who don't have a disease and treat them, you're going to dramatically increase the cost for care."
Welch also noted the negative side effects of cancer treatments. The first attempt at removing cancerous cells is usually surgery, which carries the risk of death, Welch said. Other forms of treatment, including chemotherapy and radiation, have pernicious side effects.
Physicians must also consider the psychological effects of telling patients that they have a life-threatening disease when in fact the cancer may never turn harmful, Black said.
"The biggest side effects are labeling telling someone they have the disease," he said. "It is psychologically upsetting and might affect their insurance."
Recent advances in technology have increased the problem posed by overdiagnosis, according to Black.
"Imaging is one of the technologies in medicine that has so dramatically improved, so you can see all these things you couldn't see before," Black said. "And because you [can] see these things, there is a lot of uncertainty."
To avoid problems associated with overdiagnosis, Black suggested that physicians should monitor the activity of cells instead of automatically assuming cancer and instituting an aggressive treatment plan.
"The strategies that people already have in place is, after you observe something if the patient is asymptomatic and OK before you do something or even tell the patient, you observe it," Black said. "It makes a lot of sense to do nothing but watchful waiting for a period of time."
