47 Can we identify the factors that predict the progression of DCIS to invasive cancer during mastectomy?

Background

Ductal carcinoma in situ (DCIS) identified during needle biopsy is transformed to invasive breast carcinoma (IBC) during definitive surgical excision at a rate of 15% to 50%. Current guidelines recommend an ipsilateral sentinel lymph node biopsy at the time of mastectomy performed for DCIS for preventive axillary staging in case the final pathology is outstaged. The aim of this study was to identify preoperative risk factors associated with switching to ICS in cases of final disease, to indicate which patients would most likely benefit from sentinel lymph node biopsy at the time of mastectomy.

Methods

This is a 20-year, single-institution retrospective review of women 50 years and older undergoing mastectomy as definitive surgical treatment for a preoperative diagnosis of pure DCIS with clinically negative lymph nodes. Multiple preoperative data points were examined, including imaging appearance of the lesion, multifocal or single lesion, histologic subtype of DCIS, grade, presence or absence of necrosis, history of lesions at high risk and whether or not a preoperative MRI was obtained. The LOGISTICS (SAS) procedure was used for statistical analysis.

Results

Preoperative factors and DCIS upgrade

The rate of transition from pure DCIS to invasive carcinoma at final pathology at our institution was 15%. Of the factors examined, none were statistically significant. Imaging calcifications, intermediate/high grade DCIS, and preoperative MRI use were associated with trends toward upgrade to IBC at final surgical pathology.

Conclusions

As the management of breast malignancies evolves toward a de-escalation of axillary surgery, preoperative identification of patients who would benefit from a more aggressive approach would facilitate optimal planning of surgical treatment. Our study, although not showing a predominant predictive factor for improvement in final pathology, shows promising trends that should prompt further investigation. Of particular note is that preoperative use of MRI was not associated with a lower rate of improvement in final pathology, consistent with several studies showing that routine use of breast MRI during surgery Preoperative evaluation does not improve cancer outcomes with invasive carcinoma.