Contrary to some claims, breast cancers that are detected by mammography screening do not spontaneously disappear or regress if they are not treated.
The results of a new study found that both invasive breast cancer and ductal carcinoma in situ (DCIS) will not simply vanish if left untreated.
During a 10-year period, 240 cases of invasive breast cancer and 239 cases DCIS were not treated, and none were reported to have spontaneously vanished or regressed at the time of the next mammography.
The study has been published in the Journal of the American College of Radiology.
"All lesions were described in comparison to at least one previous mammogram," said author Debra Monticciolo, MD, professor of radiology at Texas A&M University Health Sciences, Temple. "The range of follow-up is 1 to 9 years, and our intention was to demonstrate that these lesions persist."
"Of the more than 36,000 cases, we found no evidence of lesion regression," she told Medscape Medical News.
Dr. Monticciolo noted that they did not look at why the lesions were left untreated. "It could have been a range of scenarios, and that was beyond the scope of our research," she said.
Overdiagnosis From Mammography
What happens to untreated breast cancer lesions has been an issue in the fierce debates in recent years about overdiagnosis due to routine screening mammography. For example, a recent major study with a prolonged follow-up time of 17 years found that breast cancer screening does not substantially reduce the incidence of advanced cancer over time but does significantly increase the detection of nonadvanced cancers, resulting in the overdiagnosis of disease.
However, the current study was not specifically looking at overdiagnosis. "We were not trying to assess the frequency of overdiagnosis but rather to point out that delaying screening until 50 or lengthening the screening interval will not change the small amount of overdiagnosis that is known to exist," said Dr Monticciolo. "These lesions still look suspicious on subsequent mammography, as they do not disappear."
Approached by Medscape Medical News for an independent comment, Jay Baker, MD, chief, Division of Breast Imaging at Duke University Medical Center, Durham, North Carolina, also noted that outcomes of untreated lesions were not part of this research.
The study did not provide information on the outcomes of the untreated breast lesions (whether they progressed or remained indolent), but that wasn't the purpose of the paper, he said. The study wasn't able to measure or assess whether any cases were overdiagnosed or the exact amount of overdiagnosis caused by screening mammography, explained Dr Baker.
"Instead, they showed that one theoretical reason for starting mammograms later or screening less frequently — that cancers would somehow go away on their own — simply is not true and should not be used as a reason on which to base screening guidelines," he said. "I emphasize the word 'theoretical' in my answer because the studies that suggested cancers regress on their own never claimed to have direct evidence of this phenomenon."
Cancers detected by screening mammography do not spontaneously regress or disappear if left untreated. Dr Jay Baker
"The key conclusion of this study is that cancers detected by screening mammography do not spontaneously regress or disappear if left untreated," said Dr Baker. "The survey questions asked whether the untreated cancers were still visible on follow-up imaging, and all of them were still visible and none had regressed in size."
What this means is that even if a patient skipped a year of screening, those same cancers would still be visible the following year. "The precise length of follow-up may have varied for each of these cases, but the outcome was the same: None disappeared on their own," he said.
No Regression Noted
In this study, Dr Monticciolo and colleagues surveyed 108 fellows of the Society of Breast Imaging regarding untreated, screen-detected, biopsy-proven breast cancers and the associated natural history of the lesions.
Forty-two fellows (39%) responded to the survey, and the average number of screening mammograms interpreted in each practice during the past 12 months was 25,203 (range, 7000 to 75,000).
The average number of screening mammograms that were interpreted in each practice during the past 10 years was 228,844 (range, 50,000 to 700,000), yielding a total of nearly 7 million (total of 6,865,324 for all practices).
An average of 89 invasive breast cancers were detected during screening during a 12-month period, and 843 were detected over the past 10 years (range, 50 to 2500). Taken together, the total number from all practices was 25,281.
Overall, 240 cases of screen-detected invasive breast cancers were not treated, and none of them spontaneously disappeared or regressed, according to the survey respondents.
Similarly, respondents also reported that the average number of screen-detected DCIS during the past 12 months was 37 (range, 10 to 90), 347 over a 10-year period (range, 70 to 700), and a total of 9360 for all practices.
Of the screen-detected DCIS cases, 239 were not treated and none were reported to have spontaneously disappeared or regressed.
The authors and Dr Baker have disclosed no relevant financial relationships.
J Am Coll Radiol. Published online April 27, 2017. Abstract