Purpose: Ductal carcinoma in situ (DCIS) of the breast does not metastasize to axillary lymph nodes. Yet high-grade DCIS (HgDCIS) is often subjected to Sentinel Lymph Node Biopsy (SLNB) concomitant with definitive surgery. This is to avoid further axillary surgery in the event of upstaging to invasive carcinoma, which often entails Axillary Lymph Node Dissection (ALND). We wished to examine the validity of this approach.
Methods: This study includes a retrospective analysis of consecutive pre-operatively diagnosed HgDCIS patients from a single screening unit between December/2014 and August/2016. The main outcomes were the overall incidence of upstaging and the independent predictors of upstaging on multivariable analysis. The rates of various complications of SLNB vs ALND in four RCTs were used to calculate the upstaging rate below which SLNB could be safely omitted.
Results: There were 224 eligible patients of whom 26 (11.6%) were upstaged. Axillary metastasis (pN1) occurred in two patients (0.9%). On Univariable analysis, upstaged patients were significantly younger (median (IQR) = 56.0 (51.0-63) vs 60.0 (54.0-65.0); p = 0.019). Radiological size, pathological size, type of biopsy, type of operation, and comedo-necrosis were not significant (p > 0.05). On multivariable analysis, age as a continuous variable (OR 0.93; p = 0.031) and core biopsy (OR 2.62; p = 0.036) were the only independent predictors of upstaging. Chi-square test showed that patients < 55 years whose pre-operative diagnosis was made on core biopsy were at significantly higher risk of upstaging than the others (31.8% vs 9.4%; p = 0.002).
Conclusion: Upstaging of HgDCIS is infrequent. According to the known rates of complications of SLNB relative to ALND, routine SLNB concomitant with surgery seems to be more harmful than its routine omission. A selective approach based on age and type of biopsy could be considered.
Keywords: Axillary lymph node dissection; Breast carcinoma in situ; Breast screening; Mastectomy; Sentinel node biopsy.