The prevalence of
ductal carcinoma in situ (
DCIS) of the breast has increased substantially after the introduction of
breast cancer screening programs, although the clinical effects of early
DCIS detection and treatment remain unclear. The standard treatment for
DCIS has involved local
breast-conserving surgery (BCS) followed by
radiotherapy (RT) or
total mastectomy with/without endocrine
therapy, and the choice of local treatment is not usually based on clinicopathologic or
biological factors. However, we have investigated the effectiveness of local treatment using breast surgery and RT using Surveillance, Epidemiology, and End Results data, and found that the effectiveness of breast surgery was modified by the nuclear grade. Furthermore,
breast cancer-specific survival was identical between patients with low-grade
DCIS who did and did not undergo surgery. Moreover, we found that RT after BCS for
DCIS was only associated with a survival benefit among patients with risk factors for local recurrence, such as nuclear grade, age, and
tumor size. Ongoing clinical trials and translational research have attempted to develop a treatment strategy that prevents the overdiagnosis and overtreatment of low-risk
DCIS, as well as a biology-based treatment strategy for using targeted
therapy. Therefore, to develop a tailored treatment strategy for
DCIS, we need to identify molecular and biological classifications based on the results from translational research, national databases, and clinical trials.