Are there features on imaging or core biopsy that can predict tumour-positive margins after breast-conserving surgery?

Introduction

Twenty-two per cent of women required further surgery following breast-conserving surgery (BCS) in the UK in 2008 because of involved margins. This study was carried out to see whether it was possible to predict the likelihood of this from preoperative information and thus reduce the re-excision rate.

Methods

Women having BCS following a preoperative diagnosis of invasive cancer were identified from prospectively collected data at Breast Test Wales for South East Wales, over a 3-year screening round (2006 to 2009). In cases where DCIS was found at or within 2 mm of a margin, preoperative imaging was reviewed to look for peripheral calcification.

Results

One hundred and twelve out of 844 women with an invasive tumour had involved margins after BCS. Fifty-nine women had DCIS at the margin, of which 60% had calcification within 10 mm of the periphery of the tumour on mammographic review and 30% had DCIS as well as invasive cancer on core biopsy. The postsurgical pathological size was greater than the mammographic size in 79% and greater than the ultrasound size in over 90% of cases. This was not significantly changed on further review of the films. On mammographic review, 12% had dense breasts, 88% being fatty or fatty/glandular.

Conclusions

Imaging is underestimating the true size despite background breast tissue being fatty. The presence of calcification on the mammogram in such a high number of cases where DCIS is at the margin may be a useful predictor, but requires further correlation with the presence of histological calcification on the pathological specimen, which is ongoing.