Abstract
BACKGROUND: Randomized trials of radiation after breast-conserving surgery (BCS) for ductal carcinoma in situ (DCIS) found substantial rates of recurrence, with half of the recurrences being invasive. Decreasing local recurrence rates for invasive breast carcinoma have been observed and are largely attributed to improvements in systemic therapy. In this study, 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 to 2010. Cox proportional hazard models were used to investigate the association between the treatment period and recurrence, controlling for other variables. RESULTS: Overall, 363 (12%) recurrences among 2996 cases were observed. Median follow-up for patients without recurrence was 75 months (range 0-30 years); 732 patients were followed for ≥10 years. The 5-year recurrence rate for the period 1978-1998 was 13.6 versus 6.6% for the period 1999-2010 [hazard ratio (HR) 0.62, p < 0.0001]. Controlling for age, family history, presentation, nuclear grade, necrosis, number of excisions, margin status, 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, association of recurrence with treatment period persisted in those treated without radiation (HR 0.62, p = 0.003). CONCLUSIONS: Recurrence rates for DCIS have fallen over time, with increases in screen detection, negative margins, and use of adjuvant therapies only partially explaining this decrease. The unexplained decline persists in 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.