A new study published in the British Medical Journal is offering a better snapshot of the long-term risks of invasive breast cancer and death from breast cancer after ductal carcinoma in situ (DCIS) diagnosed through breast screening. Researchers examined outcomes in 35,024 women in England diagnosed with DCIS by the NHS Breast Screening Programme from its start (1988 until March 2014). They found that the rates of invasive breast cancer and the rates of breast cancer deaths were more than double the rates in the general population for at least 20 years in women who were diagnosed with DCIS.
The study revealed that women who had breast-conserving surgery had a lower rate of invasive breast cancer if they also had radiotherapy, and the lowest invasive disease rates were in women who had mastectomy.
Larger surgical margin widths were associated with a lower rate of invasive breast cancer and the same was true for endocrine treatment in women with estrogen receptor-positive disease.
In this current investigation, 13,606 women had been followed for up to 5 years, and 10,998 for 5 to 9 years as of December 2014. For longer follow-up, the numbers varied (6861 had been followed for 10-14 years, 2620 for 15-19 years, and 939 for at least 20 years). The researchers found that 2076 developed invasive breast cancer, corresponding to an incidence rate of 8.82 per 1,000 women per year. The expected national cancer incidence rates are 2.52 per 1000 women per year.
The study showed that the increased risk of disease started in the second year after diagnosis of DCIS and continued until the end of follow-up. The breast cancer death rate was 1.26 per 1,000 women per year and 70% higher than that expected from national breast cancer mortality rates.
Mannu GS, Wang Z, Broggio J, et al. Invasive breast cancer and breast cancer mortality after ductal carcinoma in situ in women attending for breast screening in England, 1988-2014: Population-based observational cohort study. BMJ. 2020;369:m1570 doi: 10.1136/bmj.m1570