A Multi- institutional Prospective Analysis of Impact of CanAssist Breast (Morphometric Immunohistochemistry Based Test) on Adjuvant Chemotherapy Decisions in Early Breast Cancer

Abstract Purpose: CanAssist Breast (CAB) has been validated retrospectively for assessing risk of recurrence and thereby usefulness of chemotherapy in HR+/HER2- breast cancer. The objective of this study is to assess the agreement between physician’s treatment plan and CAB risk stratification and evaluate whether CAB results aid in the physician’s treatment decision. Methods: The data on the physician’s treatment plan before and after the CAB test was collected prospectively between 2016 and 2021 in 249 patients. Changes in treatment recommendations and compliance with CAB reports were analyzed. Results: Based on conventional clinicopathological features physicians planned to treat 46% of patients with endocrine therapy (ET) (low-risk-LR)), 24% with chemoendocrine therapy (CET) (high-risk-HR)) and in 30% physicians were uncertain of prescribing chemotherapy (intermediate-risk-IR)) before CAB testing. The correlation between clinical risk assessment and CAB risk stratification (k=0.2 (0.05-0.35) was nonsignificant. CAB classified 64% as LR, which was 18% (9.3-25, P=0.0001) higher compared to clinical LR. In the clinical IR category, CAB risk proportions were 55:45 (LR: HR). We observed a substantial shift in treatment recommendation from CET to ET in 54% (40.75- 66.84, P<0.0001) of clinical HR and ET to CET in 26% (18.27- 35.01, P<0.0001) of clinical LR patients. Overall CAB lead to change in treatment recommendation in 42% of the cohort. Conclusions: There was a significant impact of CAB on the physician’s treatment decision. CAB provided definite treatment recommendation to IR patients where the physician had dilemma on prescribing chemotherapy and provided precise treatment plan to clinical LR and HR patients.