P5-12-02: Vacuum Assisted Biopsies of Ductal Carcinoma In Situ and Concordance with Post-Operative Histology: Implications for the Low Risk DCIS Trial.
Authors: Soumian S , Down SK , Roked F , Chaudhri S , Francis A 
Published: June 2012

Aim The enormous increase in the diagnosis of ductal carcinoma in situ (DCIS) by the NHS Breast screening has not lead to an expected decrease in the incidence of invasive breast cancer. It is not clear if all grades of DCIS progress inexorably to invasive cancer if left untreated. There is recognition that DCIS is overtreated, ie if left alone may not cause harm during the woman's lifetime. In the absence of new clinical trial data, surgery still remains the universal treatment. It is known that a higher proportion of patients with screen detected DCIS receive mastectomy than those with screen detected invasive cancer. Recently a randomized trial called the Low risk DCIS Trial has been proposed which intends to specifically compare the current treatment of low grade DCIS ie surgery with active monitoring using annual mammography. In order to effectively implement this, concordance between diagnostic biopsy and excision histology is vital and therefore vacuum assisted mammotome biopsy (VAB) and a central pathology review of diagnostic biopsy specimens prior to randomization will be mandatory. Therefore, in this study, we assessed the concordance between diagnostic biopsies performed by VAB technique and the post operative histology for DCIS in our institution.

Methods Retrospective data of all diagnostic breast biopsies specifically using the VAB technique with the primary diagnosis of DCIS from year 2001 to 2010 in our institution was collected. Both screening and symptomatic patients were included. Concordance between diagnostic histology and post operative excision histology was assessed for high, intermediate and low grade DCIS. Demographic details and potential factors influencing concordance including number of cores taken and lesion size were also collected for analysis.

Results A total of 161 cases were identified out of which 102 (63%) were of high grade, 35 (22%) of intermediate grade and 24 (15%) were of low grade histology. In the High grade group, the concordance with final histology was 70% (72/102). In this group, the diagnosis was upgraded to invasive carcinoma in 21% (21/102). 9% (9/102) were downgraded to intermediate or low grade. In the intermediate grade group, the concordance with final histology was 66% (23/35). In this group, the diagnosis was upgraded to invasive carcinoma in 11% (4/35) and to high grade in 17% (6/35). 6% (2/35) were downgraded to low grade. In the low grade group, the concordance with final histology was 71% (17/24). In this group, the diagnosis was upgraded to intermediate grade in 17% (4/24) and invasive carcinoma in 12% (3/24). All factors associated with lack of concordance were noted.

Conclusion Concordance between VAB diagnostic biopsies of high, intermediate and low grade DCIS and post operative histology is good in this series and is to our knowledge the first to be reported using only large volume biopsies by VAB techniques. This audit has identified possible factors influencing the lack of concordance and these results with concordance data from other UK centres will be used by trial pathologists to refine protocols for the Low risk DCIS trial.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P5-12-02.