What's the best procedure for women who have been diagnosed with the type of breast cancer called ductal carcinoma in situ (DCIS)? Should they undergo surgery to remove only the lesion, radiation, mastectomy or just have more frequent mammograms? There doesn't seem to be a clear answer, and the latest research has given rise to conflicting opinions.
DCIS lesions are found in the milk ducts of the breasts, and are considered to be non-invasive; they tend not to spread beyond these ducts. In fact, some experts have suggested that DCIS not even be considered cancer. But most do, though perhaps an indolent type.
Before mammography screening became common in the 1970s and 80s, only about three percent of breast cancers detected were identified as DCIS, pointed out editorialists Drs. Laura Esserman and Christina Yan, from the University of California, San Francisco. Now, they say, DCIS makes up 20 to 25 percent of cancers detected by screening. Thus, it has become more important to establish clear guidelines for its evaluation and treatment.
The important question centers around the long-term effect of DCIS, specifically: Does it shorten women's lives? That was the question addressed by Dr. Steven A. Narod of the Women's College Research Institute in Toronto, Ontario, and his colleagues. These investigators performed a retrospective, observational study of over 100,000 women who had received a diagnosis of DCIS between 1988 and 2011, using data from the Surveillance, Epidemiology, and End Results (SEER) database. They determined the risk of dying from breast cancer 10 and 20 years post-DCIS diagnosis, and also examined the effects of age at diagnosis, race, and various treatment paradigms.
In brief, the main outcome of the study was that the risk of dying from breast cancer was very low in women diagnosed with DCIS whether or not they had been treated. Twenty years post-diagnosis, that risk was 3.3 percent over all, although it was significantly higher (7.8 percent) for women diagnosed at 35 years of age or younger, compared to older women, and was also significantly higher for black women compared to non-Hispanic white women (7.0 vs. 3.0 percent). If, however women experienced a later occurrence of invasive cancer in the breast with DCIS, their risk of dying of breast cancer was significantly elevated to 18 percent.
The investigators point out that although some have described DCIS as a "noninvasive precursor lesion that cannot metastasize or cause death," the majority of women who did die of breast cancer didn't have an incidence of invasive breast cancer just DCIS. Further, preventing invasion by radiation therapy or mastectomy didn't prevent death from breast cancer.
These authors concluded: "Some cases of DCIS have an inherent potential for distant metastatic spread," and thus should definitely be considered as "defacto breast cancers" rather than as simply pre-invasive markers.
"So, the question is," asked ACSH senior nutrition fellow Dr. Ruth Kava, "how can we tell which DCIS lesions will lead to invasive cancers? This is a similar problem we see with prostate cancer some of these are indolent and don't raise the risk of spreading to other tissues, but we can't tell which are dangerous.
"Obviously we must have more research to help us make these distinctions," she continues. "On the other hand, the results of this study do indicate that treating DCIS with mastectomy or radiation has no significant impact on the risk of dying from breast cancer and women should be made aware of that when deciding what to do about the condition."