Ductal carcinoma in situ linked to higher long-term risks of breast cancer, mortality
Among women who had surgery for ductal carcinoma in situ, rates of developing invasive breast cancer later were lower with more intensive treatment and larger final surgical margins, an English study found.
While women with ductal carcinoma in situ (DCIS) diagnosed through breast screening are at increased risk for invasive breast cancer and breast cancer death, more intensive treatment and resection may help lower the risk of the former, an observational study found.
Researchers looked at data from 35,024 women in England diagnosed with DCIS by the National Health Service Breast Screening Programme from its start in 1988 until March 2014. Through the program, women in specified age groups receive personal letters every three years inviting them to attend an appointment for screening mammography. The main outcome measures were incident invasive breast cancer and death from breast cancer. Results were published May 27 by The BMJ.
By December 2014, 13,606 women had been followed for up to five years, 10,998 for five to nine years, 6,861 for 10 to 14 years, 2,620 for 15 to 19 years, and 939 for at least 20 years. Overall, 2,076 women developed invasive breast cancer, corresponding to an incidence rate of 8.82 (95% CI, 8.45 to 9.21) per 1,000 women per year, which was more than double that expected from national cancer incidence rates (ratio of observed rate to expected rate, 2.52; 95% CI, 2.41 to 2.63). This increase began in the second year after DCIS was diagnosed and continued until the end of follow-up. Three hundred ten of these 2,076 women died of breast cancer, corresponding to a death rate of 1.26 (95% CI, 1.13 to 1.41) per 1,000 women per year, which was significantly higher than expected from national breast cancer mortality rates (ratio of observed rate to expected rate, 1.70; 95% CI, 1.52 to 1.90).
The breast cancer death rate was similar to that expected from national mortality rates during the first five years after DCIS diagnosis but increased thereafter. The observed-to-expected ratios for mortality rates were 1.98 (95% CI, 1.65 to 2.37), 2.99 (95% CI, 2.41 to 3.70), and 2.77 (95% CI, 2.01 to 3.80) in years five to nine, 10 to 14, and 15 or more after DCIS diagnosis, respectively. Of 29,044 women with unilateral DCIS who had surgery, rates of invasive breast cancer were lower among those who had more intensive treatment (i.e., mastectomy, radiotherapy for women who had breast-conserving surgery, and endocrine treatment in estrogen receptor-positive disease) and those with larger final surgical margins.
Limitations of the study included the inability to compare breast cancer incidence or mortality in women who were screened but had no abnormality identified, the study authors noted. They added that the data contained some missing values, that information on treatment and tumor-related factors was available only from the year 2000 onward, and that information for final margin status was available only from 2007 onward.
The authors noted that in the U.K., surveillance of women after a DCIS diagnosis focuses on the first few years afterward. “We have, however, provided evidence of the long term nature of the risk of invasive disease after a diagnosis of DCIS, even for women with low or intermediate grade disease,” they wrote.
A cover story in the June ACP Internist focused on what clinicians need to know about dense breasts, a risk factor for breast cancer. The story explains the four categories of breast density, what each one might mean clinically, and how to communicate this information to patients in a way that increases understanding while decreasing fear.