O. Kantor1, C. Pesce2, C. H. Wang3, E. Liederbach2, D. J. Winchester2, K. Yao2 1University Of Chicago,Department Of Surgery,Chicago, IL, USA 2Northshore University Health System,Department Of Surgery,Evanston, IL, USA 3Northshore University Health System,Center For Biomedical Research Informatics,Evanston, IL, USA
Introduction:
The rates of neoadjuvant chemotherapy (NAC) are increasing in the US. We hypothesized that more women are undergoing bilateral mastectomy (BM) after NAC then similar women not undergoing NAC for early stage breast cancer.
Methods:
The National Cancer Data Base was used to identify women with invasive, clinical stage I-II breast cancer that underwent either neoadjuvant or adjuvant chemotherapy from 2006-2012.
Results:
262,732 patients with clinical stage I-II breast cancer that had either NAC or adjuvant chemotherapy were identified. Of these, 45,972 (17.5%) had NAC prior to surgery – 5.5% of clinical stage I tumors and 27.6% of clinical stage II tumors. BM rates amongst those with cT1, cT2 and cT3 tumors were 23.4%, 20.8%, and 22.0%, respectively for those undergoing NAC compared to 13.6%, 15.8%, and 20.9% for those undergoing adjuvant therapy (p<0.01). From 2006 to 2012, BM rates among cT1 tumors went from 8.8% to 17.9%, for cT2 tumors from 9.7% to 22.4% and for cT3 tumors from 13.1% to 27.4% (all p<0.01). For those patients who had a partial or complete pathologic response after NAC, BM rates increased an additional 6.5% for cT1 tumors (p<0.01), and <1% for cT2 or cT3 tumors (p>0.05).
From 2010-2012, overall BM rates for triple negative tumors was 18.0% and for Her2 positive tumors 18.1%. NAC increased rates of BM most in patients with triple negative tumors (9.2%) compared to 7.5% for Her2 positive tumors and 6.8% for luminal A tumors (p<0.01). On multivariate analysis adjusting for patient, facility, tumor, and treatment factors, the effect of NAC persisted, with NAC increasing the odds of BM in patients with cT1 tumors (OR 1.63, CI 1.52-1.76) and cT2 tumors (OR 1.29, CI 1.22-1.35), but not in cT3 tumors (OR 1.02, CI 0.89-1.18).
Conclusion:
The use of neoadjuvant chemotherapy significantly increases the rate of bilateral mastectomy in early stage breast cancer. This is most pronounced in cT1 tumors amenable to breast conservation.