Abstract P2-18-05: Delayed chemotherapy in HER2 positive breast cancer

Introduction: It is always a great concern when breast cancer treatment is delayed for a variety of reasons such as patient personal situation, medical conditions, insurance issues and scheduling difficulties. Most studies regarding delayed cancer treatment focus on chemotherapy and the findings are conflicting. This study aimed to determine the rate of delayed neoadjuvant or post-operative adjuvant chemotherapy/targeted treatment in HER2 amplified breast cancer at a single institution and examine its effects on survival outcomes including relapse free survival (RFS), overall survival (OS), breast cancer specific survival (BCSS) and distant metastatic free survival (DMFS). Methods: Patients with a tissue diagnosis proven HER2 amplified breast cancer who were surgically treated at the Revlon/UCLA Breast Center between 2002 and 2018 were included. Patients with a previous history of breast cancer, metastasis and no follow-up were excluded. Patients without clear dates of diagnosis, surgery, beginning and end of chemotherapy and radiation were excluded for further analysis. Delayed neoadjuvant chemotherapy with target treatment was defined as greater than 2 months from the time of tissue diagnosis and delayed adjuvant treatment was defined as greater than 2 months from the last cancer surgery. Chi-squared test was used to compare the differences of clinicopathologic characteristics between the two groups: delayed and non-delayed. Kaplan-Meier curve and log-rank test was used to identify candidate prognosticators and Cox-regression analysis was used to identify independent prognosticators for survival outcomes. Results: Of the 322 cases surgically treated at the Revlon/UCLA Breast Center, 101 had neoadjuvant, 168 had adjuvant, 5 were unknown and 48 had no chemotherapy/target treatment. Median follow-up was 74.5 months. In the entire studied population, OS was significantly better in the groups who received either neoadjuvant or adjuvant chemotherapy/target treatment than those who did not (HR 0.0248; 95% CI, 0.086-0.711). In the neoadjuvant group, 11 (11.5%) had delayed start. Breast conserving surgery was more frequent in the delayed group (63.6%) and mastectomy was more frequent in the non-delayed group (72.6%). In addition, clinically positive node was more frequent in the non-delayed group (p=0.001). Residual cancer in the breast was associated with worse RFS (p=0.027). Residual nodal metastasis was associated with inferior RFS (p=0.012), OS (p=0.012), BCSS (p=0.037) and DMFS (p=0.011). In multivariate analysis, pCR was associated with better OS (HR 6.329, 95% CI, 1.354-29.586). In the adjuvant group, 38 (22.6%) had delayed chemotherapy/target treatment which was found to be negatively associated with RFS (HR 6.707; 95% CI, 1.224-36.769). Conclusion: Delayed chemotherapy/target treatment in HER2 positive breast cancer appeared to occur more frequently in the adjuvant group than the neoadjuvant group. In the adjuvant group, delayed start of chemotherapy/target treatment negatively impacted survival. In the entire cohort and surgery first group, those who did not receive adjuvant chemotherapy/target treatment had worse survival than those who did. Taken together, chemotherapy/target treatment should be considered in all patients with HER2 positive breast cancer and neoadjuvant treatment is preferred to minimize any possible delay in starting chemotherapy/target treatment. Citation Format: Ho Hur, Amy Le, Helena R Chang. Delayed chemotherapy in HER2 positive breast cancer [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P2-18-05.