Recurrence rates for ductal carcinoma in situ: Analysis of 2,996 patients treated with breast-conserving surgery over 30 years.
32 Background: Randomized trials of radiation after breast-conserving surgery (BCS) for DCIS found substantial rates of recurrence, with half of recurrences invasive. Decreasing local recurrence rates for invasive breast carcinoma have been observed, and are largely attributed to systemic therapy improvements. Here we examine recurrence rates after BCS for DCIS over 3 decades at one institution. Methods: We retrospectively reviewed a prospectively maintained database of DCIS patients undergoing BCS from 1978–2010. Cox proportional hazard models were used to investigate the association between treatment period and recurrence, controlling for other variables. Results: 363 (12%) recurrences among 2996 cases were observed. Median follow-up for patients without recurrence was 75 months (range 0–30 years); 732 were followed for ≥ 10 years. The 5-year recurrence rate for 1978–1998 was 13.6% versus 6.6% for 1999–2010 (hazard ratio [HR] 0.62, p < 0.0001). After controlling for age, family history, presentation (radiologic vs clinical), nuclear grade (non-high vs. high grade), necrosis, number of excisions ( ≤ 2 vs ≥ 3), margin status (positive/close vs negative), radiation, and endocrine therapy, treatment period remained significantly associated with recurrence, with later years associated with a lower HR (0.74, p = 0.02) compared to earlier. After stratification by radiation use, and adjustment for 7 other factors, the decrease in recurrence rates was limited to those without radiation (HR 0.62, p = 0.003); there was no decline in recurrence rates among those receiving radiation (HR 1.13, p = 0.6). Conclusions: Recurrence rates for DCIS have fallen over time. Increases in screen-detection, negative margins, and use of adjuvant therapies only partially explain the decrease. The unexplained decline is limited to women not receiving radiation, suggesting it is not due to changes in radiation efficacy, but may be due to improvements in radiologic detection and pathologic assessment. The lower recurrence risk observed for DCIS patients treated in more recent years is important for patient education, especially in view of the widely reported recent increase in use of mastectomy.