A retrospective single-center study investigating the clinical significance of grade in triple-negative breast cancer.

Abstract

e13108 Background: Triple negative breast cancer is defined as estrogen (ER), progesterone (PR), and human epidermal growth factor receptor (HER-2) proteins negative. The grade is the degree of similarity of tumor cells to normal cells under microscope and is an important biomarker of overall patient outcomes or prognosis with higher grades having a poor prognosis. As recent chemotherapy trials noted moderately undifferentiated grade 2 tumors showing higher rates of relapse, we hypothesize that grade can also be a predictive biomarker or determinant of response to specific treatment. Methods: We reviewed 305 patient charts of triple negative breast cancer patients from 2004-2017 at Windsor Regional Cancer Center analyzing the significance of grade with respect to oncological variables, survival-time, and time to relapse. Statistical analysis was performed using Fleming-Harrington, Pairwise Testing, and COX regression, where applicable. Results: Univariate analysis showed statistically significance difference in chemotherapy type (P = 0.008) and a marginal one in ER & hormone therapy status (P ~0.09) between the grades. The overall survival rates were 90.12%, 64.4%, and 77.2%, for grade 1, 2, 3 respectively. The overall difference in survival among the three groups was statistically significant, based on Fleming-Harrington test (P = 0.019). Comparing only between grade 2 and grade 3, we found that after five years, grade 2 patients had a 5.5-fold increased risk of death (HR = 5.5; 95% CI 1.2-25.6) and 2-folds higher risk of relapse (HR = 1.9; 95% CI 1.1-3.2). Grade 3 does significantly better than grade 2 in time to relapse with relapse rates of 70%, 55.6 %, and 75.6%, respectively for grades 1, 2, and 3 (P = 0.04). Conclusions: Tumor grade has a significant positive predictive value in determining relapse with grade 2 tumors demonstrating poorer disease-free survival as compared to grade 1 & 3, less time to relapse, and increased risk of death. This has implications in stratifying triple negative breast cancer patients by grade in future clinical trials while ongoing research yields new targets for chemotherapy.