SOURCES: Steven Narod, M.D., senior scientist, Women's College Research Institute, and professor, School of Public Health and Department of Medicine, University of Toronto; Sarah Hawley, Ph.D., M.P.H., professor, Division of General Medicine, and co-founder of CanSORT, the Cancer Surveillance and Research Team, University of Michigan Medical School, Ann Arbor; Aug. 20, 2015, JAMA Oncology, online
THURSDAY, Aug. 20, 2015 (HealthDay News) -- Only 3 percent of women diagnosed with an early stage of breast cancer will die of their disease within 20 years, and more aggressive treatment does not improve that high survival rate, a new study suggests.
"The good news is that death is pretty rare," said study first author Steven Narod, director of the Familial Breast Cancer Research Unit at Women's College Research Institute, in Toronto. "Clinically, the fact is that 3 percent in the big picture should be reassuring."
The researchers did find that the death rates for both younger women and black patients diagnosed with this early stage cancer were higher.
The early stage breast cancer that they studied is ductal carcinoma in situ (DCIS), a small, localized cluster of cancer cells. About 20 to 25 percent of breast cancers that mammogram screening detects are DCIS. It is considered a stage 0 cancer that does not escape its location in the breast, the researchers said. Cancer that spreads into the rest of the breast or beyond is considered invasive.
"One clinical implication is to reiterate that DCIS is not an 'emergency,' " said Sarah Hawley, a cancer research specialist at the University of Michigan in Ann Arbor. "The study supports that the risk of dying is extremely low for these patients."
Narod and his co-authors combed through a database of information on slightly more than 108,000 women who had been diagnosed with DCIS between 1988 and 2011. They compared these patients' risk of dying from breast cancer with the risk for women in the general population. On average, the women were 54 years of age when they received their DCIS diagnosis, and the authors followed their outcomes for an average of 7.5 years. The team then estimated overall death rates at 10 and 20 years.
In all, 956 women in the study ultimately died of breast cancer. Of those, 517 never had invasive cancer in the breast after treatment seemed to cure their DCIS. That means that the cancerous breast cells from their DCIS had escaped at some point and survived in the lungs or bone, later developing into a deadly cancer, Narod explained.
The study authors also found that women with a history of DCIS had about the same rates of invasive breast cancer in either breast, not just the breast where the DCIS was detected.
Women with DCIS usually undergo either surgical removal of the cancerous area followed by radiation therapy, removal alone or complete removal of one or both breasts. The study authors found that the addition of radiation therapy did not appear to save any more lives compared to just surgery alone.
"The finding that radiation treatment did not impact survival for most DCIS patients suggests that alternatives to radiation should be considered, including omitting it altogether," Hawley said.
The findings were published online Aug. 20 in the journal JAMA Oncology.
Hawley noted that women under age 35 and black women had a higher risk of death from DCIS. In the broadest analysis, younger women had a mortality risk of almost 8 percent, and the risk for black women was 7 percent.
In an accompanying editorial, Laura Esserman and Christina Yau, both from the University of California, San Francisco, wrote that DCIS looks different in younger women, causing symptoms such as a detectable mass or bloody nipple discharge. Because screening in women under age 40 is rare, they said, these symptoms are usually how younger women end up on the clinical radar.
Some other risk factors for a rogue DCIS include whether or not it responds to hormones, carries certain versions of cancer-related genes or is 2 inches across or larger.
These risk factors have yet to lead to different treatments for younger women or black women who are diagnosed with DCIS. Hawley said that with further research, more targeted treatments might be possible for women who are at higher risk.
Narod suggested that for populations with the highest risk, at some point, chemotherapy might become an option to deal with DCIS cells that may be lingering somewhere outside the treated breast.
In spite of some heightened concerns for specific high-risk groups, the results are generally promising for women who receive a DCIS diagnosis. Narod points out that the overall risk of dying because of DCIS is "not as bad as having a family history of breast cancer or high-density breast tissue."
Indeed, Esserman and Yau viewed the results as a reason to reduce a sense of urgency. They write that "given the low breast cancer mortality risk, we should stop telling women . . . that they should schedule definitive surgery within two weeks of diagnosis."
Visit the U.S. National Cancer Institute for more on breast cancer.