OBJECTIVES/SPECIFIC AIMS: Treatment of breast cancer surgery can be classified into two overall groups: Breast-Conserving Therapy (BCT) (including partial mastectomy (PM) and oncoplastic surgery (OS)) and MAST (including mastectomy (M) and M with breast reconstruction (M+R)). Breast reconstruction (OS or M+R) offers patients an improved quality of life by aesthetically symmetric breast, higher patient satisfaction and reduced re-excision rates. Furthermore, subgroups of M+R, mastectomy with implant placement (M+I) has doubled to 21%, meanwhile mastectomy with muscular flap reconstruction (M+MF) has declined to only 2% of overall breast cancer intervention. Furthermore, in patients with with ductal carcinoma in situ (DCIS), published national guidelines recommend that sentinel lymph node biopsy (SLNB) should be offered when treated with M and should not be offered when treated with BCS. Overall complication rates for breast cancer surgery vary depending on short-term or long term outcome but are approximately 2-40%. Mortality and overall morbidity are overall low in less than 5% of cases. Known wound or infectious complications have been associated with smoking, radiation, obesity and diabetes. Nevertheless, other patient comorbidities and surgical predictors influencing acute postoperative complications are contentious. Single institutional studies or reviews compared single or two groups of breast cancer interventions for post-operative complication rates. Few studies with large enough patient cohort to analyze all possible variables influencing post-operative acute complications following all breast cancer surgeries. Understanding surgical complications is crucial to patient safety and improving health outcomes. Therefore, this study examines the 30-day postoperative complication rates in breast cancer patients who underwent a PM, M, M+R, or OS. Using the NSQIP database, we aim to elucidate these surgical trends and complications trends, while expanding our understanding of predictive surgical factors. We also examined appropriate axillary management associated with surgical interventions between 2005 and 2016. METHODS/STUDY POPULATION: A retrospective cohort analysis was conducted using the ACS-NSQIP database from 2005 to 2017. All participant user files (PUF) were obtained and approved by ACS NSQIP. The Tufts Medical Center Institutional Review Board deemed this study exempt from institutional review, given ACS NSQIP database is a de-identified data set. Inclusion criteria for this study were women with classified post-operative diagnosis of invasive breast cancer (IBC) or ductal carcinoma in-situ (DCIS) breast cancer who underwent either any BCT or any MAST procedure. Post-operative diagnosis was classified according International Classification of Diseases Ninth/Tenth Revision (ICD-9/10) code for IBC or DCIS. Surgical (M, PM, OS, M+R) and axillary lymph node categorization were done using CPT codes known for each intervention. Exclusion criteria included males, benign breast surgery, surgery for benign breast disease, lobular carcinoma, patients undergoing breast cancer surgery with 2 CPT codes with ambiguous category placement and septic patients at time of surgery. For each intervention, a total of 16 complications were clustered into 8 groups and examined over the 13-year period. ALN management was categorized as follows: no intervention on ALNs, or ALN surgery (SLNB or ALN dissection (ALND)). Chi-square tests were performed for demographic and complication rate analysis. Smoothed linear regression and non-parametric Mann- Kendall test assessed complication trends. Uni-variate and multivariate logistical regression were computed to associate odd’s ratio for comorbidities, surgical predictors and patients demographics. RESULTS/ANTICIPATED RESULTS: A total of 226,899 patients met the inclusion criteria. Annual breast surgery trends changed as follows: PM 45.6% to 45.9 (p=0.21), M 36.8% to 25.5% (p=0.001), M+R 15.7% to 23.6% (p=0.03) and OS 1.8% to 5.0% (p=0.001). Analyzing the patient cohort who underwent breast conservation, categorical analysis showed a decreased use of PM alone (96% to 90%) with an increased use of OS (4% to 10%). For the patient cohort undergoing mastectomy, M alone decreased (69% to 52%); M+R with muscular flap decreased (9% to 2%); and M+R with implant placement increased (20% to 41%) – all 3 trends p<0.0001. The rate of ALN management has changed as follows: SNLB or ALND significantly increased in mastectomy patients from 53.6% to 69.5% (SS 1.5%, R2 0.69, p < 0.01), while it changed little in the BCS population: 22.5% to 26.4% (SS 0.4%, R2 0.18, p = 0.09). Complication rates have steadily increased in all mastectomy groups (p< 0.05) but not in BCT. Cumulative complication rates between surgical categories were significantly different in each complication cluster (all p<0.0001). Overall complication rates were: PM: 2.25%, OS: 3.2%, M: 6.56%, M+MF: 13.04% and M+I: 5.68%. The most common predictive risk factors were mastectomy interventions, increasing operative time, ASA class and BMI, smoking, recent weight loss, history of CHF, COPD and bleeding disorders (all p<0.001). Patients who were non-diabetic, younger (<60) and treated as outpatient all had protective OR for an acute complication (p<0.0001). DISCUSSION/SIGNIFICANCE OF IMPACT: The modern era of breast surgery is identified by the increasing use of reconstruction for patients undergoing breast conservation (in the form of OS) and mastectomy (in the form of M+R). Despite national recommendations for the management of axillary lymph nodes in patients undergoing breast surgery for DCIS, nearly 30% of cases continue to be mismanaged: more than 30% of patients with DCIS undergoing mastectomy fail to receive SLNB, and more than 26% of DCIS patients undergoing BCS are still receiving axillary lymph node surgery. Our study provides data showing significant trends that will impact the future of both breast cancer surgery and breast training programs. We also provide data comparing nationwide acute complication rates following different breast cancer surgeries that can be used to inform patients during surgical decision making.