Long-term outcomes of women with large DCIS lesions treated with breast-conserving therapy

Purpose The paucity of data on women with large (>= 40 mm) DCIS tumors lead to uncertainty on the safety of breast-conserving surgery (BCS) for these patients. We evaluated the impact of large tumor size on local recurrence (LR) among women with DCIS treated with BCS +/- radiotherapy (RT). Methods Treatment and outcomes were ascertained through administrative databases for all women with DCIS in Ontario from 1994 to 2003 treated with BCS +/- RT with negative margins; 82% had pathology review. Cox proportional hazards model was used to evaluate the impact of tumor size on LR. 10- and 15-year LR-free survival (LRFS) were calculated using Kaplan-Meier method. Results The cohort includes 2049 women treated by BCS (N = 1073 with RT). Median follow-up is 14 years (IQR 9-17 years). Referenced to tumors <= 10 mm, the risk of LR following BCS was significantly higher for larger tumors: HR >= 40 mm = 3.67 (95% CI 2.13, 6.33; p < 0.001), HR 26-39 mm = 2.27 (95% CI 1.47, 3.50, p < 0.001), and HR 11-25 mm = 1.42 (95% CI 1.06, 1.92, p = 0.02). However, for individuals with BCS + RT, large tumor size was not associated with a significantly increased risk of LR (HR >= 40 mm = 1.92 (95% CI 0.97, 3.79); HR 26-39 mm = 1.81 (95% CI 1.09-2.99)). For women with tumors >= 40 mm, 10-year LRFS risk for those treated by BCS alone, BCS + RT without boost, and BCS + RT with boost was 58.9%, 82.8%, and 83.9%. Conclusion Large DCIS lesions >= 40 mm are associated with higher risks of LR following BCS, but high long-term LRFS rates can be achieved with the addition of breast RT.

Automated summary

The lack of data on women with large DCIS tumors leads to uncertainty regarding the safety of breast-conserving surgery for these patients. This study found that larger tumor size is associated with a higher risk of local recurrence following BCS, but the addition of breast radiotherapy can achieve high long-term LRFS rates.