Researchers say the mortality rate for women with DCIS is "too low to justify toxic therapy."
DCIS is diagnosed when cancer cells are identified in the milk ducts of the breast but have yet to spread to any surrounding tissue, meaning they are unable to metastasize outside the breast.
Some women diagnosed with DCIS will go on to develop invasive breast cancer and some will die from the disease, but at present, there is no way to determine which women will do so. As such, the majority of women with DCIS undergo breast-conserving surgery or mastectomy, usually followed by radiotherapy.
However, the new research from Dr. Steven Narod, of Women's College Hospital in Toronto, Canada, and colleagues suggests such treatment may be unnecessary for many women with DCIS, after finding it is unlikely to reduce risk of death from the cancer.
To reach their conclusion, the team analyzed data from the Surveillance, Epidemiology and End Results (SEER) database, identifying 108,196 women aged 15-69 who were diagnosed with DCIS between 1988 and 2011.
The researchers calculated the 10- and 20-year breast cancer-specific mortality rate for the women, comparing them with those of women among the general US population.
In addition, the researchers investigated how treatment for DCIS influenced breast cancer-specific mortality.
Compared with women in the general population, the team calculated that women diagnosed with DCIS were at around 1.8 times greater risk of breast cancer death. The 10-year and 20-year breast cancer-specific mortality rates among women with DCIS were 1.1% and 3.3%, respectively.
The researchers found the death rate was higher for black women and women who were diagnosed with DCIS before the age of 35.
Mortality rate 'too low to justify toxic therapy'
The team says the most important finding, however, was that preventing invasive DCIS through treatment did not appear to influence breast cancer-specific death rates.
Overall, the women's 20-year risk of ipsilateral invasive recurrence of DCIS - developing of invasive cancer on the same side of the body - was 5.9%, while the risk of contralateral invasive DCIS recurrence - invasive cancer on the opposite side of the body - was 6.2%.
While women who underwent breast-conserving surgery followed by radiotherapy had a lower 10-year risk of ipsilateral invasive recurrence - at 2.5% vs 4.9% - they experienced no reduction in 10-year breast cancer-specific mortality, at 0.8% vs 0.9%.
What is more, while women who had a single-breast mastectomy had a lower risk of ipsilateral invasive recurrence at 10 years than those who had breast-conserving surgery - 1.3% vs 3.3% - they had a higher 10-year breast cancer-specific mortality rate, at 1.3% vs 0.8%.
Overall, the team identified 517 women who died from breast cancer after DCIS diagnosis, despite never developing invasive breast cancer.
Although the team's findings show women diagnosed with DCIS are more likely to die from breast cancer, Dr. Narod says they also suggest surgery and radiotherapy may be unnecessary:
"This paper effectively redefines our understanding of the early stages of breast cancer and shows that the cancerous behavior is present very early on. There is a potential for chemotherapy to reduce the rates of death from DCIS but for most women the mortality rate (less than 2%) is too low to justify toxic therapy."
In an editorial linked to the study, Dr. Laura Esserman and Christina Yau, PhD, of the University of California-San Francisco, say Dr. Narod and colleagues have conducted an "impressive analysis" based on SEER data.
As a result of increasing evidence indicating women diagnosed with DCIS are at low risk of breast cancer death, the authors say it may be time to change how health care professionals approach the condition.
"The community of radiologists and surgeons needs to be part of the call for change," they add. "Given the low breast cancer mortality risk, we should stop telling women that DCIS is an emergency and that they should schedule definitive surgery within 2 weeks of diagnosis."
Earlier this month, Medical News Today reported on a study suggesting chemotherapy is unlikely to prolong survival for breast cancer patients aged 80 and older.