Prognostic Ability of the Indication for Adjuvant Systemic Therapy Based on Preoperative Biopsy and the Surgical Excision Specimen in Cases of Small Breast Tumors (CONSCIENCE): A Retrospective Cohort Study.

Abstract

Purpose: To evaluate the agreement between clinical and pathological assessments of tumor size and grade in patients with small, luminal type breast cancer.

Methods: This retrospective monocenter cohort study included women treated for clinical stage 1, estrogen receptor positive, HER2 negative breast cancer between January 2020 and July 2023. Preoperative and postoperative assessments of tumor size, malignancy grade and lymph node status were compared. The impact on the indication to administer systemic therapy was evaluated. Statistical analyses included agreement estimates expressed as proportions with 95% confidence intervals.

Results: 292 patients were examined preoperatively and postoperatively. Agreement for tumor grade was 81% (95% CI [76-85]) and for tumor size based on ultrasonography (US) 75% (95% CI [70-80]. Tumor size was more likely underestimated than overestimated by US (17% vs 8%). Twelve percent of cN0 patients had a SLN containing metastases. The preoperative assessment for adjuvant chemotherapy aligned with postoperative recommendations in 93% of patients and for adjuvant endocrine therapy in 75%. Preoperative underestimation of the indication to administer chemotherapy and endocrine therapy occurred in 7% and 18% of all patients respectively. A positive SLN contributed to these proportions of underestimated systemic treatment indications in half of these groups.

Conclusion: Our study demonstrates disagreement between preoperative and postoperative assessment of malignancy grade and tumor size in approximately one fifth of the patients. Absence of postoperative information of primary tumor characteristics would have led erroneously to omission of adjuvant chemotherapy in less than 5% of the patients.