Treatment options for ductal carcinoma in situ and the risk of invasive breast cancer

The authors aimed to determine the effect of different treatments on the risk of developing invasive breast cancer (IBC) in women diagnosed with ductal carcinoma in situ (DCIS). The authors concluded that there was an interaction between age and follow-up period on IBC risk and that the benefit of radiation seemed to be smaller among younger women. 

Ductal carcinoma in situ (DCIS) is an early stage of breast cancer in which the cancer cells are confined to the milk ducts. Due to increased screening measures, the rates of women treated for DCIS have also increased. DCIS is generally treated with mastectomy (surgical removal of the breast) or breast conserving surgery (BCS; the removal of part of the breast) combined with radiation. DCIS is treated in order to reduce the risk of invasive breast cancer (IBC), the spread of cancer cells into the breast tissue. However, whether or not aggressive treatment of DCIS decreases the risk of IBC is not entirely clear.

The aim of this study was to determine the effect of different treatments on the development of IBC in women diagnosed with DCIS. 

Information on 10,090 women included in a cancer registry was examined in this study. The average follow-up time was 10.7 years. 4,820 patients were treated with initial mastectomy. 5,270 women initially received BCS. Of these, 50% also received radiation.

5.2% of patients who underwent BCS and radiation would eventually undergo mastectomy after 15 years. In comparison, 12% of patients who underwent BCS alone would undergo mastectomy.

After an average of 5.8 years, 588 women developed IBC in the same breast. After 15 years, the incidence of IBC was 1.9% after mastectomy, 8.8% after BCS and radiation and 15.4% after BCS alone.

Women over 50 years who underwent BCS alone were 4.44 times more likely to develop IBC compared to women who also underwent radiation. Women less than 50 years were 2.11 times more likely to develop IBC if they were not treated with radiation. After 5 years of follow-up, there was no difference in risk of IBC for women under 50.

536 women developed IBC in the opposite breast (6.4% after 15 years, 8.9% after 20 years). The risk of developing IBC in the opposite breast was not associated with treatment type.

The authors concluded that there was an interaction between age and follow-up period on IBC risk and that the benefit of radiotherapy (RT) seemed to be smaller among younger women.