1. Increased Postoperative Complications in Bilateral Mastectomy Patients Compared to Unilateral Mastectomy: An Analysis of NSQIP Database Osman F, Saleh F, Corrigan M, Jackson T, Cil T. University of Toronto, Toronto, Canada

2. Introduction Introduction The rate of contralateral prophylactic mastectomy among women with unilateral breast cancer has increased Incidence of contralateral breast cancer is very low Post-operative complications: Bilateral > Unilateral?

3. Method Unilateral and Bilateral Mastectomies with SLNB 4,219 Unilateral Mastectomy with SLNB 3, 722 Bilateral Mastectomy with SLNB 497 ACS- NSQIP Data 2007-2010 All Mastectomy Patients N= 20,322 Ambiguous coding and Missing Data N= 714 Other procedures (Reconstruction, Axillary dissection etc.) N= 12, 769 Two Sentinel Node Biopsy Code N= 1,426 High Risk Pre-operative Characteristics Steroids, Infections Dialysis, Etc. N= 1194

4. Results: Baseline Characteristics Unilateral Mastectomy and sentinel lymph node biopsy N (%) Bilateral Mastectomy and sentinel lymph node biopsy N (%) P-Value N = 4,2193,722(88.2)497 (11.8)N/A Mean Age (  SD)64.2 (13.0)58.6 (11.8)P<0.001 Hypertension1,979 (50.1)182 (39.1)P<0.001 ASA b P=0.020 ASA 1177 (4.5)26 (5.6) ASA 22,362 (59.8)306 (65.8) ASA 31,363 (34.5)130 (28.0) ASA 446 (1.2)3 (0.7) Diabetic509 (12.9)37 (8.0)P<0.002 Mean BMI (  SD) c 28.4 (6.9)29.2 (7.1)P=0.024 Coronary Artery disease185 (4.7)15 (3.2)P=0.193 COPD d 145 (3.7)9 (1.9)P=0.060 ETOH e 49 (1.2)5 (1.1)P=1.000 Smoker a 565 (14.3)65 (14.0)P<0.846 Chemotherapy f 48 (1.2)13 (2.8)P=0.011

5. Results Complication Unilateral Mastectomy and SLNB N (%) Bilateral Mastectomy and SLNB N (%) OR (95% CI) Overall Complications ** 164 (4.2)39 (7.6)1.9 (1.3 –2.8) Wound ** 106 (2.9)29 (5.8)2.1 (1.3- 3.3) Infectious ** 29 (0.8)11 (2.2)2.9 (1.3- 6.0) Respiratory5 (0.1)0 (0.0)(0.0, 5.8) Thromboembolic10 (0.3)1 (0.2)0.7 (0.0, 5.3) Renal1 (0.03)0 (0.0)N/A Neurologic3 (0.1)1 (0.2)2.5 (0.04, 31.2) Cardiac2 (0.1)0 (0.0)0.0 (0.0, 14.4) Bleeding15 (0.4)0 (0.0)0.0 (0.0, 1.9) **P-value <0.05

6. Multivariable Analysis of Overall Complications OR (95% CI)P-Value Bilateral vs. Unilateral mastectomy with sentinel lymph node biopsy 1.9 (1.3- 2.8)0.001 Age1.01 (1.00 - 1.02)0.132 Diabetes1.3 (0.9 - 1.9)0.213 Smoker2.2 (1.5 - 3.2)<0.001 Body Mass Index1.1 (1.0 - 1.1)<0.001 Chronic obstructive pulmonary disease 1.3 (0.7 - 2.4)0.495 Coronary artery disease1.4 (0.8 - 2.5)0.246 Hypertension1.0 (0.7 - 1.4)0.900 ASA 3 and 4*1.0 (0.8 - 1.5)0.721 Chemotherapy0.9 (0.2- 3.8)0.877

7. Limitations of the Study Only Short-term outcomes (30-day) Cancer stage not reported in NSQIP data Procedural codes: CPM No Reconstruction

8. Conclusion Bilateral mastectomy appears to be associated with an increased risk of overall post-operative wound and other infections. Further studies are warranted to examine short term and long-term complications of CPM and whether these complications delay treatment.