Reuben S. Mezrich, MD, of the University of Maryland School of Medicine in Baltimore, presented a lecture on the controversies of screening in general, and specifically on the controversies surrounding mammography at the 93rd annual meeting of the Radiological Society of North America (RSNA).
In overview on the justification for screening for all modalities, Mezrich said that there are four questions should always be asked: How do we best perform the exam? Who should be screened? What is the follow-up process? Who gets paid for the follow-up? For example, one recent issue arose with CT colonoscopy. Mezrich said that “relatively high false-positives rates have a major negative effect” with CT colonoscopy, so the radiologists in that field need to take that into consideration.
He cited from a 2005 study published in Radiology about virtual colonoscopy, which examined 500 patients. Of those patients, 315 had extracolonic findings, and 45 had clinically important findings. These findings caused a debate about whether screening is warranted.
According to Mezrich, the criteria for screening should include:
- The potential disease has serious consequences;
- The screening population has a high prevalence of detectable preclinical phase, which can justify the cost of screening;
- The screening test detects little pseudo-disease, which appears to be disease on the screening test, but is not;
- The screening test should have high accuracy for detecting the detectable; the screening test must detect disease before critical point;
- The screening test should cause little morbidity; the screening test should be affordable and available;
- The treatment is more effective when applied before symptoms begin; and
- The treatment is not too risky or toxic.
In order to defend the necessity of mammography, Mezrich cited critiques from Samuel S. Epstein, MD, professor emeritus of environmental and occupational medicine at the University of Illinois School of Public Health, and chairman of the Cancer Prevention Coalition, who said that mammograms are ineffective and can cause cancer. In response, Mezrich said there are worries about radiation, but now instead of 1 rad. in previous mammograms, the newer equipment only delivers 0.2 rad. Equipment from 20 years ago delivers 10 times the dosage.
Mezrich submitted that “we are getting hysterical about radiation doses unnecessarily – it carries a risk in less than one in one million.” He also said that Epstein’s suggestion that the compression of a mammogram could spread or burst the tumor, which Mezrich said there is no clinical proof that mammograms can spread cancer. In regards to a tumor bursting, he said it has “never happened,” he said.
Regarding Epstein’s concerns that mammograms missed too many cancers, Mezrich said, “here he has a point, especially in women with dense breasts, who have sensitivity of as low as 40 percent compared to women with fatty breasts,” and dense breasts are more common in younger women. Epstein also questioned the specificity of mammograms. In response, Mezrich said the results mirror the sensitivity, typically there is “higher specificity with older, fatty breasts, as opposed to younger, denser breasts.”
He said that over the last decade, mortality due to breast cancer has dropped from 50 percent to 38 percent, according to a study published in the October 2005 issue of the New England Journal of Medicine. Mezrich said that the “decreased mortality is due to increased screening.”
He concluded that mammography “does save lives, it is effective, so even though it has drawbacks, it is still quite effective and until, a new modality appears, it is the best of all available options.”