But the researchers also found an increased tendency for women to seek removal of both breasts, despite their analysis that cancer survival rates remained similar regardless of the form of treatment.
The findings, published online this month in the Journal of the National Cancer Institute, raise new questions in the ongoing debate about the best way to treat the non-invasive, yet potentially early cancer cells that define DCIS.
“With this analysis, we sought to determine what treatment women selected when diagnosed with DCIS, and whether there was any impact in mortality with the different treatments,” said senior author E. Shelley Hwang, M.D., chief of breast surgery at the Duke Cancer Institute.
“This is an important women’s health issue, and we still do not have enough data around what the best treatment is,” Hwang said. “Studies like ours should be viewed as a call for well-designed clinical trials that could provide more information to better guide both doctors and patients.”
Hwang and colleagues used data from the Surveillance, Epidemiology, and End Results (SEER) program in the United States and analyzed more than 121,000 cases between 1991 and 2010 in which women were diagnosed with DCIS.
The researchers found that in general, patients have opted for less extensive surgery over time, with rates of single mastectomy declining to 19.3 percent from 44.9 percent, while rates of lumpectomy and radiation increasing to 46.8 percent from 24.2 percent. Sentinel node biopsies were also increasingly used instead of the more extensive axillary dissections, in which numerous lymph nodes are removed.
Those trends, however, are accompanied by a rise in double mastectomies, from 0 percent to 8.5 percent, often among younger women.
Differences in overall survival were associated with the types of treatment, indicating that differences in general health may impact treatment choice. The highest 10-year overall survival rate (89.6 percent) was observed among patients who underwent lumpectomy combined with radiation, followed by mastectomy (86.1 percent) and lumpectomy alone (80.6 percent).
But when the researchers focused specifically on breast cancer deaths at 10 years, they found virtually identical rates between the treatment groups. Ten-year breast cancer survival rates were 98.9 percent for those who underwent lumpectomy plus radiation, 98.5 percent for mastectomy and 98.4 percent for lumpectomy alone.
“One of the things we wanted to examine was what happened to these women after they were diagnosed with DCIS,” Hwang said. “Overall, 9.2 percent of all deaths were due to breast cancer. However, the predominant cause of death was not breast cancer, but cardiovascular disease, which accounted for 33 percent of all deaths.”
Hwang said the exception was among women younger than age 50 with DCIS, where one-third of deaths resulted from breast cancer, highlighting the importance of aggressive treatment for those patients.
“What our study shows is that we urgently need clinical trials to know whether we are doing the right thing for this group of patients,” Hwang said. “This is not a question of providing no treatment or providing overly aggressive treatment, it’s an issue of providing the right individualized treatment for a group of patients with an excellent prognosis regardless of what treatment they receive. We need more and better evidence for the therapies we recommend to each individual patient to make sure that our interventions are indeed benefiting them.”
In addition to Hwang, study authors include Mathias Worni; Igor Akushevich; Rachel Greenup; Deba Sarma; Marc D. Ryser; and Evan R. Myers.
Contact: Sarah Avery