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

Background: Triple negative breast cancer (TNBC) is a heterogenous cancer type which lacks the receptors for estrogen (ER), progesterone (PR), and human epidermal growth factor receptor (HER-2) proteins. Comparatively, HER-2 positive cancers currently have a 7 year disease-free survival rate of 93% while in triple negative breast cancers, it can be as low as 77%. Purpose: While histological tumor grade or the degree of similarity to normal cells is an important prognostic factor (overall outcome), there is limited information on its predictive value (effect of specific therapeutic intervention). This project aimed to investigate the predictive value of grade in triple negative breast cancer for clinical decision making regarding treatment. Experimental Design: We reviewed 305 patient charts of triple negative breast cancer patients from 2004-2017 at Windsor Regional Cancer Center and the significance of grade with respect to oncological variables, survival-time, and time to relapse were explored. Results: The overall survival rates were 90.12%, 64.4%, and 77.2%, for grade 1, 2, 3 respectively. 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). Conclusion: Grade can be shown to have positive predictive value in determining relapse with grade 2 showing poorest disease-free survival and faster time to relapse after the 5-year mark with implications in stratifying patients by grade in future clinical trials as further research elucidates more information about molecular differences between grades, as an explanation for these findings