Study Examines Factors Associated with Early-Stage Breast Cancer Mortality

An observational study of more than 100,000 women with a diagnosis of ductal carcinoma in situ (DCIS, or Stage 0 breast cancer) and published in JAMA Oncology, showed that age and ethnicity are important risk factors for death from breast cancer following a DCIS diagnosis, according to findings that estimated the 10- and 20-year mortality in this patient population. 

Some women with breast cancer experience a second breast cancer (DCIS or invasive), and a small proportion of patients with DCIS will die of breast cancer. It is not clear, however, what factors predict mortality after a DCIS diagnosis. Women who develop ipsilateral breast cancer recurrence have an increased risk of death but some women die of breast cancer without first receiving a diagnosis of local invasive disease, wrote the researchers.

Steven A. Narod, MD, FRCPC, Women’s College Research Institute (Toronto, Canada) and colleagues used the Survey, Epidemiology, and End Results 18 registries database to identify women diagnosed with DCIS from 1998 to 2011. The study included 108,196 women whose risk of dying of breast cancer was compared to that of women in the general population. The mean age at diagnosis was 53.8 years, and the mean duration of follow-up was 7.5 years. 

The estimated 10-year breast cancer-specific mortality rate after diagnosis of DCIS was 1.1% and the rate at 20 years was 3.3%. The risk of dying of breast cancer for all women who had a DCIS diagnosis was increased by 1.8 times compared with the general population. At 20 years, women who received a diagnosis before age 35 had a higher mortality rate compared with older women (7.8 vs 3.2, respectively; hazard ratio [HR], 2.58; 95% confidence interval [CI], 1.85-3.60; P<.001). Black women also had an increased rate of mortality compared with non-Hispanic white women (7.0% vs 3.0%, respectively; HR, 2.55, 95% CI, 2.17-3.01; P<.001).

One finding of greatest clinical importance was that preventing ipsilateral invasive recurrence did not prevent death from breast cancer, according to the researchers. Women who developed this recurrence were 18.1 more likely to die of breast cancer than women who did not. Among all patients, the risk of ipsilateral invasive recurrence at 20 years was 5.9% and the risk of contralateral invasive recurrence was 6.2%. For patients who had a lumpectomy, the use of radiotherapy reduced the risk of developing an ipsilateral invasive recurrence from 4.9% to 2.5% but did not reduce the cancer-specific mortality at 10 years (0.9% vs 0.8%, respectively). Similarly, patients who had unilateral mastectomy had a lower risk of ipsilateral invasive recurrence at 10 years than patients who underwent a lumpectomy (1.3% vs 3.3%, respectively) but had a higher breast cancer-specific mortality (1.3% vs 0.8%, respectively). A total of 517 women died of breast cancer following a DCIS diagnosis but did not experience an invasive cancer in the breast prior to death.

The researchers concluded that outcome of breast cancer mortality for DCIS patients is important and studies on potential treatments that affect mortality are warranted.—Eileen Koutnik-Fotopoulos

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Narod SA, Iqbal J, Giannakeas V, Sopik V, Sun P. Breast cancer mortality after a diagnosis of ductal carcinoma in situ [published online ahead of print August 20, 2015]. JAMA
Oncol
. doi:10.1001/jamaoncol.2015.2510.