Abstract P6-06-24: Intact p53 can predict more hormonal therapy benefit in invasive breast cancer: Evaluation of interactions between immunohistochemical p53 status and adjuvant therapy

Abstract

Abstract Background: To confirm the prognostic and predictive values of p53 accumulation, particularly in invasive breast cancer patients sorted according to subgroup based on immunohistochemical hormone receptor (HR) and HER2 status. Methods: A total of 15,598 immunohistochemical data for p53, ER, PgR, and HER2 were retrospectively retrieved from the web-based database of the Korean Breast Cancer Society. Overall survival (OS) and breast cancer-specific survival (BCSS) were calculated and compared with the Kaplan-Meier method with log-rank test. Multivariate analyses were performed using a stratified Cox proportional hazard regression model. A model evaluating interactions between p53 and both hormonal therapy and chemotherapy was used to determine the treatment benefit from both modalities. Results: Prognostic value of p53 was most significant in the HR+/HER2- subgroup for OS and BCSS, with hazard ratios of 1.44 (95% CI, 1.08-1.93) and of 1.47 (95% CI, 1.09-1.99). The hazard ratios for p53 overexpression had borderline significance in the HR+/HER2+, and were invalid in the HR-/HER2+ and HR-/HER2- subgroups. The model with interaction terms revealed that hormonal therapy significantly interacts with p53 status (p = .002 and .007 for OS and BCSS), resulting in an insignificant prognostic value of p53 status (p = .268 and .296 for OS and BCSS). An interaction between chemotherapy and p53 status was not found in this model. Conclusion: p53 overexpression has independent prognostic value, particularly in the HR+/HER2- invasive breast cancer, which is most likely caused by differential treatment benefits from hormonal therapy depending on p53 status. Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P6-06-24.