Overdiagnosis of Cancer Causing Harm to Some Patients
A review of cancer diagnosis and outcomes suggests that overdiagnosis of cancer through improved screening methods may be causing harm to patients. Cancers found on CT scans, colonoscopy, mammogram, and with PSA (prostate specific antigen) testing may help some individuals, but many cancers are being diagnosed that may never cause symptoms.
H. Gilbert Welch, M.D. and William Black, M.D., of the Dept. of Veterans Affairs Medical Center, White River Junction, Vt. and the Dartmouth-Hitchcock Medical Center analyzed data from cancer screening trials to find the incidence of overdiagnosis of cancer.
The results showed that approximately 25 percent of breast cancers found on mammograms and roughly 60 percent of prostate cancers detected with prostate-specific antigen (PSA) tests could represent overdiagnosis.
The findings were qualified by scientist when they compared the incidence of mortality related to diagnosis of thyroid, prostate, kidney and breast cancer, and melanoma over the past 30 years. There have been increases in diagnosis of the five types of cancers, but not an increase in deaths.
A suggestion from the reviewers is to educate patients about the chances of cancer being overdiagnosed as the result of sophisticated screening tools that include virtual colonoscopy. Abnormalities in tissue found outside the colon can lead to even more testing.
The authors write, "Whereas early detection may well help some, it undoubtedly hurts others. Often the decision about whether or not to pursue early cancer detection involves a delicate balance between benefits and harms…different individuals, even in the same situation, might reasonably make different choices."
Another solution to limit overdiagnosis of cancer is to raise the threshold for reporting abnormalities, as is the current practice adopted with lung nodules that show up on CT scans.
The study of genomics might help. "It is possible that new insights from genomics will ultimately allow us to more accurately predict tumor behavior at the individual level," the authors write. "However the field has not advanced to that point yet. We must explore other clinical strategies."
Overdiagnosis of cancer can lead to harm for some patients, leading to unnecessary testing that may also carry risks and are costly. The scientists are urging for better guidelines to eliminate the problem. CT scans; colonoscopy, MRI, and other advanced imaging techniques can detect cancer early, but as is the case with prostate and breast cancer, found in the study, many detected cancers might never cause symptoms or require treatment.