Abstract Background: BREAST-Q is a widely accepted patient reported outcome measure (PROM) for breast surgery patients. BREAST-Q has been challenging to implement for clinical practice, due to insufficient understanding of clinical factors influencing BREAST-Q scores and lack of reference values for score interpretation. As a result, the clinical applicability of the BREAST-Q is limited, and benefits of routine PROM implementation on care quality have not been realized for breast surgery patients. This study finds predictors impacting long-term scores for the BREAST-Q Breast Conserving Therapy (BCT) module and determines reference values to guide score interpretation in clinical practice. Methods: A retrospective review of BCT patients at Memorial Sloan Kettering Cancer Center was conducted. All patients completed at least one BREAST-Q in 2018-2020. Patient characteristics were collected, including age, BMI, race, smoking status, chemotherapy, radiation therapy (RT), and axillary surgery (sentinel lymph node biopsy, axillary lymph node dissection). BREAST-Q was collected routinely during clinical visits as part of standard of care. Linear regression measured the impact of patient characteristics on 1 year and 2 year BREAST-Q scores. Median scores at baseline and 2 weeks, 6 months, 1 year, and 2 years after surgery were determined for RT and No RT patients. Pearson’s Chi-square and Student t-tests were used for categorical and continuous variables, respectively. Based on prior literature, a minimal clinically important difference of 4 points was used (scale 0-100). Results: 1866 BCT patients were included. Average age was 58.9(11.4) with BMI of 27.9(6.4). Patients were primarily white (76.8%) and non-smokers (89.7%); 36.8% had chemotherapy, 74.7% had axillary surgery, and 73.3% had RT. Regression analysis showed age and race as significant predictors of Satisfaction with Breast and Physical Wellbeing scores (Table 1). RT was a clinically significant predictor for Physical Wellbeing, reducing scores by 4.5 points at 1 year and 4.6 points at 2 years. Reference values were then created for RT and No RT patients. (Table 2). Conclusions: This study found factors impacting satisfaction and physical wellbeing after BCT using BREAST-Q scores of a longitudinal cohort of women and presented references values for score interpretation. Separate reference values were created based on RT as it is a significant predictor of BREAST-Q scores and omission of RT is increasingly offered to older women with low-risk breast cancer, given no survival benefit. These reference values can be incorporated into a user-friendly application or integrated into electronic medical records to help patients and physicians interpret BREAST-Q scores in a clinically meaningful way. Future research should assess the impact of early interventions targeting BCT patients below the 25th percentile (e.g. referrals to plastic surgeons or physical therapy) on BREAST-Q scores. Table 1.Multivariate analysis of BREAST-Q score predictors at 1 year and 2 years after surgerySatisfaction with BreastPhysical Wellbeing1 year2 year1 year2 yearScore changeSEp-valueScore changeSEp-valueScore changeSEp-valueScore changeSEp-valueAge0.1533.907p=0.0020.1280.068p=0.0610.2800.041p < 0.0010.2930.054p < 0.001BMI0.0190.0483p=0.821-0.2200.119p=0.065-0.0120.073p=0.867-0.1380.093p=0.141RaceWhiteReference--Reference--Reference--Reference--Black-7.3462.018p < 0.001-11.4652.876p < 0.001-7.4821.748p < 0.001-6.6512.259p=0.003Asian-1.4631.936p=0.450-1.5842.842p=0.578-2.2221.677p=0.185-0.3472.248p=0.878Other-3.7162.998p=0.2150.7904.451p=0.859-7.4672.575p=0.004-4.1963.495p=0.230Unknown1.4962.804p=0.5946.2213.914p=0.1120.2342.410p=0.923-1.9253.074p=0.531Smoking StatusNeverReference--Reference--Reference--Reference--Previous-1.2161.174p=0.300-1.4221.603p=0.375-1.5821.013p=0.119-1.0301.259p=0.414Current-1.7752.584p=0.492-3.3293.946p=0.399-3.8962.238p=0.082-8.0853.099p=0.009Unknown6.7652.384p=0.0059.4784.054p=0.1120.7612.064p=0.7136.1623.183p=0.531ChemotherapyNoReference--Reference--Reference--Reference--Yes-0.7401.148p=0.5190.3961.603p=0.805-3.3750.993p < 0.001-1.8101.262p=0.152Radiation TherapyNoReference--Reference--Reference--Reference--Yes-0.8961.293p=0.488-2.8961.830p=0.114-4.4951.118p < 0.001-4.6431.435p=0.001Axillary SurgeryNoReference--Reference--Reference--Reference--Yes-0.3581.319p=0.786-1.8711.948p=0.337-3.9091.140p < 0.001-3.6461.526p=0.017 Table 2.BREAST-Q reference values at 2 weeks, 6 months, 1 year, and 2 years after surgeryBaseline2 Weeks6 Months1 Year2 YearsRTSatisfaction with Breastsn=445-n=485n=1223n=65325th percentile53-63615950th percentile64-78757275th percentile82-100100100Physical Wellbeingn=483n=843n=486n=1228n=65125th percentile726060606650th percentile857176717675th percentile10082898989Psychosocial Wellbeingn=445-n=487n=1221n=65125th percentile62-66646650th percentile71-83838375th percentile87-100100100Sexual Wellbeingn=417-n=430n=1108n=58025th percentile46-48484850th percentile62-66666675th percentile70-798484No RTSatisfaction with Breastsn=172-n=186n=439n=22925th percentile48-67.5636350th percentile64-88827875th percentile82-100100100Physical Wellbeingn=184n=323n=188n=442n=23025th percentile726066717650th percentile897176828975th percentile1008289100100Psychosocial Wellbeingn=174-n=187n=437n=23025th percentile64-71666950th percentile74-87878775th percentile93-100100100Sexual Wellbeingn=161-n=158n=387n=19925th percentile43-535354.550th percentile62-66666675th percentile74-919191 Citation Format: Jacqueline J Chu, Jonas A Nelson, Paula Garcia, Babak J Mehrara, Andrea L Pusic, Monica Morrow, Mary L Gemignani, Audree B Tadros. Satisfaction and physical wellbeing after breast conserving therapy: Clinical predictors and reference values using the BREAST-Q [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P3-18-06.