A Comparison of the Risks of In-Breast Recurrence after a Diagnosis of Dcis or Early Invasive Breast Cancer

(1) Background: It is controversial whether ductal carcinoma in situ (dcis) is a preinvasive marker of breast cancer or if it is part of a spectrum of small cancers with malignant potential. Comparing clinical outcomes in women with invasive and noninvasive breast lesions might help to resolve the issue. (2) Methods: From a database of 2641 patients with breast cancer, we selected women who had been treated with breast-conserving surgery for a cancer that was 2.0 cm or less in size, node-negative, and nonpalpable. No subject received chemotherapy. Cancers were categorized as noninvasive (stage 0, n = 172) or invasive (stage 1, n = 401) based on a review of the pathology records. We compared the actuarial risks of in-breast recurrence after invasive and noninvasive breast lesions before and after adjusting for tamoxifen and radiotherapy. (3) Results: The 18-year cumulative risk of in-breast recurrence was 35.2% for patients with dcis and 12.8% for patients with small invasive cancers (hazard ratio: 2.4; 95% confidence interval: 1.5 to 3.8; p < 0.0003). After adjustment for radiotherapy and tamoxifen treatment, the difference was small and nonsignificant (hazard ratio: 1.4; 95% confidence interval: 0.9 to 2.4; p = 0.22). (4) Conclusions: For women with small, nonpalpable, node-negative breast cancers, the likelihood of experiencing an in-breast recurrence was associated with radiotherapy and with tamoxifen, but not with the presence of cancer cells invading beyond the basement membrane.