Abstract P1-15-07: Improved Outcomes of Breast-Conserving Surgery (BCS) and Radiation Therapy (RT) for Ductal Carcinoma In Situ (DCIS)

Abstract

Abstract Background: DCIS patients treated at our center from 1976 to 1990 had an actuarial 10-year local recurrence (LR) rate of 15%. Since then, improved mammographic and pathologic evaluation and greater attention to achieving negative margins may have translated to lower risk of LR following BCS + RT for DCIS. However, the clinical implications of hormone-receptor and HER2 status in DCIS remain unclear. We sought to determine 1) if LR rates following BCS + RT have improved with this more modern approach, 2) the relation between the LR rate and HER2 status, and 3) clinical and pathologic factors associated with HER2+ tumors. Methods: We reviewed records of 246 consecutive patients who underwent BCS and adjuvant RT for DCIS at a single academic institution from 2001 to 2007. The median age at diagnosis was 54 years. One hundred and forty-one patients (57%) were postmenopausal and 226 (92%) were diagnosed after routine screening mammogram. Fifty percent of patients underwent re-excision. The median volume of excised tissue was 78 cm3 (interquartile range, 43-143 cm3) and the median number of tissue blocks with DCIS was 3 (interquartile range, 2-7). Forty tumors (16%) were grade I, 110 (45%) were grade II and 96 (39%) were grade III. Final margins were negative (>2 mm) for 222 patients (90%), close (≥2 mm) for 23 (9%) and positive for 1 (0%). The median dose to the whole breast was 44 Gy (range, 40-52 Gy) and 244 (99%) received a boost to the primary site of median dose 16 Gy (range, 8-18 Gy). Routine estrogen-receptor (ER), progesterone-receptor (PR), and HER2 testing was instituted in 2003. Of the 163 patients with HER2 testing, 33 (20%) had HER2+ tumors (3+ on immunohistochemistry). Of the 186 patients with ER and/or PR testing, 174 (94%) had ER and/or PR+ tumors and of these, 104 (60%) received adjuvant hormonal therapy. Logistic regression was used to evaluate the association of clinical and pathologic factors with HER2 status. Results: With a median follow-up period of 58 months (range, 4.2-110 months), there were no LRs among the 246 patients. Seven patients (3%) developed contralateral breast cancer, of which 4 were invasive and 3 were in situ. Seven patients (3%) died of causes unrelated to breast cancer. On univariate analysis, HER2+ was significantly associated with grade III, ER-/PR-, central necrosis, comedo subtype, more extensive DCIS (based on the number of tissue blocks with DCIS), and postmenopausal status. When adjusted for ER/PR and grade, postmenopausal status remained significantly associated with HER2+ (odds ratio 3.3; 95% CI 1.2-8.7; p=0.019). Conclusions: In an era of routine detailed mammographic and pathologic evaluation, widely negative margins and the use of a boost to the primary site in patients with DCIS, we observed no local recurrences with a median follow-up time of 58 months, even among patients with HER2+ DCIS. Factors associated with HER2+ tumors included postmenopausal status and more extensive DCIS, as well as grade III, ER-/PR-, central necrosis, and comedo subtype. Further follow-up and additional studies are required to confirm these results. Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P1-15-07.