Public-health efforts to increase the use of breast-cancer screening appear to have altered the types of breast cancer being diagnosed

October 01, 2017

Both trends suggest that widespread mammography screening, along with improvements in imaging technology and increased biopsy rates, among other factors, are catching breast cancer earlier, before it starts to spread and becomes more life-threatening, according to a new study by Christopher Li, M.D., Ph.D., and colleagues at FSince 1980, the incidence of ductal carcinoma in situ, or DCIS, one of the most common kinds of early stage breast cancer, has increased more than sevenfold. This sharp increase in DCIS ?? which is a tumor that contains cancer-like cells but is not considered "true" cancer because the cells have not invaded normal breast tissue ?? has been accompanied by a flattening in the incidence of true invasive breast cancer.

"Some small studies do indicate that women with LCIS are equally likely to develop cancer in one or both breasts, so oftentimes it is considered a nonsurgical disease, because the only logical treatment would be a bilateral mastectomy, which would be unnecessary in the vast majority of cases," Li said. "However, if we could develop new tools to predict which women with LCIS are more likely to develop invasive cancer we could better counsel them on what might be appropriate treatment options," he said.

LCIS is characterized by precancerous changes in the cells that line the milk-producing lobules, or lobes, of the breast. The condition cannot be felt during an exam or seen on a mammogram, and so it is typically found by chance during a breast biopsy performed for another reason.

In contrast, because ductal carcinoma in situ, or DCIS, is common, accounting for more than 14 percent of U.S. breast-cancer cases, clinical randomized trials have shown that women benefit from treatment. The most common treatments for DCIS are either breast-conserving surgery with radiation or total mastectomy.

In DCIS, the cells lining the milk ducts have cancer-like characteristics. If left untreated, DCIS may, over time, become cancerous and begin to spread, or invade, the surrounding milk ducts.

"Given that rates of DCIS and LCIS continue to increase in the United States, clinically useful tools that improve our abilities to stratify these patients based on their risk of invasive cancer are needed," Li and colleagues wrote.

According to the American Cancer Society, more than 58,400 new cases of in situ breast cancer are expected to occur among women this year. Of these, approximately 85 percent will be DCIS.

The study was based on data from 32,990 women diagnosed with DCIS and 5,462 women diagnosed with LCIS between 1980 and 2001. Cases were identified through nine population-based cancer registries that participate in the Surveillance, Epidemiology, and End Results, or SEER, Program, which is funded by the National Cancer Institute. The registries represented women from Connecticut, Hawaii, Iowa, New Mexico, Utah, and the metropolitan areas of Atlanta, Detroit, San Francisco-Oakland and Seattle-Puget Sound. The NCI funded the research.