Abstract 4297: Racial/ethnic disparities in breast cancer radiosensitivity
Authors: Wright Jean L. , Reis Isildinha , Zhao Wei , Takita Cristiane , Poitevien Martine , Hu Jennifer 
Published: August 2012

Abstract
Purpose: To evaluate radiotherapy (RT)-related skin toxicity and its relationship to quality of life (QOL) outcomes in a tri-racial/ethnic cohort. Methods: We evaluated the first 172 patients in an ongoing prospective study of conservatively managed breast cancer patients using the validated Breast Cancer Treatment Outcome Scale (BCTOS) questionnaire to assess RT-related QOL, and NCI CTCAE v3.0 criteria to assess skin toxicity (ST). BCTOS was completed prior to and at RT completion, and skin toxicity was assessed at week 3 and RT completion. We recorded patient demographics, body mass index (BMI), disease and treatment characteristics and used Student's t-test and regression for statistical analysis. We divided BCTOS parameters into 3 domains: physical appearance/function, personal reaction to RT, and worst pain in the last 4 weeks. Results: Completed BCTOS questionnaires were available for 145 patients (84%) included in this analysis. Patients were 17.2% non-Hispanic white (NHW), 60.7% Hispanic white (HW), 19.3% black (B), and 2.8% other. 18.6% had DCIS, 52.4% stage I, and 29% stage II-III invasive breast cancer. 30.3% had BMI &lt;25, 28.3% 25-29.99, and 41.4% γ30. All patients had BCS followed by RT +/− systemic therapy; median breast dose 50 Gy + 10 Gy boost. At RT completion, all patients had ST: 46.2% Grade (Gr) 1, 50.3% Gr 2, and 3.4% Gr 3. In the entire cohort, there was a significant increase from baseline to RT completion in all QOL domains: Post minus baseline mean difference in physical appearance/function was 7.7 points (p&lt;0.001), personal reaction to RT 8.1 points (p&lt;0.0001), and pain 3.9 points (p&lt;0.001). For physical appearance/function, greater differences were found with higher ST grade (10.4 for Gr 2/3 vs. 4.5 for Gr 1, p=0.01), by race (15.6 points for B vs. 5.9 points for HW and 5.3 points for NHW/other, p=0.003), and increasing BMI (3.6 for &lt;25, 6.8 for 25-29.99, and 11.2 for α30, p=0.019). For worst pain in last 4 weeks, greater differences were found with increasing BMI (1.8 for &lt;25, 2.8 for 25-29.99, and 6.1 for α30, p=0.037) and borderline significant increase with ST grade (2.3 for Gr 1 vs. 5.2 for Gr 2/3, p=0.057). There were no significant differences in personal reaction to RT. With respect to physical appearance/function, there was significant interaction between race/ethnicity and BMI (p=0.015). Among women with BMI α30, there were significant effect of B race (p=0.010) and worst toxicity grade (p=0.02). Conclusion: In a diverse cohort of breast cancer patients, RT affected all QOL domains of the BCTOS. RT-induced ST was more common among B patients and those with higher BMI and correlated with physical appearance/function and pain. Underlying etiology for variation in RT-related breast symptoms is unknown and may relate to genetic, biologic, and/or environmental factors. Our ongoing study with a targeted sample size of 1,000 may shed light on the mechanisms of racial/ethnic disparities in RT outcomes of breast cancer patients.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4297. doi:1538-7445.AM2012-4297