Patterns of care for ductal carcinoma in situ of the breast: Queensland's experience over a decade.

OBJECTIVES: To review management of ductal carcinoma in situ (DCIS) of the breast in Queensland, with reference to breast conserving surgery (BCS) and adjuvant radiation therapy (RT). In addition, we examined the incidence of invasive breast cancer recurrence and factors predictive of invasive recurrence.

MATERIALS AND METHODS: A retrospective review of the Queensland Oncology Repository identified women with resected DCIS (TisN0) ± adjuvant RT between 2003 and 2012. Time to invasive breast cancer recurrence was analysed using the Kaplan Meier method. Median follow-up was 4.9 years.

RESULTS: 3038 women had surgery. 940 (31%) had mastectomy and 2098 (69%) underwent BCS. Of 2098 women having BCS, 1100 (52%) received BCS alone and 998(48%) received adjuvant RT. The use of RT significantly increased over the decade from 25% to 62% (p=<0.001). Clinicopathological factors associated with RT use on multivariate analysis included age ≤70, higher socioeconomic status, larger tumour size, higher nuclear grade and surgical margins ≤5 mm. Invasive breast cancer recurrence at 5 years was 1.7% [95% CI 1.0-3.0] in RT group versus 2.8% [95% CI 2.1-3.8] in BCS alone group. Factors associated with increased risk of invasive recurrence on multivariate analysis were age <40 and surgical margins ≤2 mm.

CONCLUSION: The use of adjuvant RT in Queensland significantly increased between 2003 and 2012. Selection of patients for RT was based on clinicopathological factors associated with higher recurrence risk. Although longer follow-up is required, the selective use of radiation therapy after BCS is associated with a low rate of invasive breast cancer recurrence at 5 years.