Background: Pathologic complete response after neoadjuvant chemotherapy (NACT) correlates with overall survival (OS) in primary breast cancer. A recently described staging system based on pre-treatment clinical stage (CS), final pathological stage (PS), estrogen receptor (ER) status and nuclear grade (NG) leads to a refined estimation of prognosis in unselected patients. Its performance in luminal type breast cancers has not been determined. This study investigates the clinical utility of this CPS+EG score when restricted to hormone receptor-positive (HR+)/human epidermal growth factor receptor 2-negative (HER2-) patients and compares the results to a cohort of unselected patients.
Methods: The CPS+EG score was calculated for 6637 unselected patients and 2454 patients with HR+/HER2- tumours who received anthracycline/taxane-based NACT within 8 prospective German trials.
Results: Five-year disease-free survival (DFS) and OS were 75.6% and 84.1% for the unselected cohort and 80.6% and 87.8% for the HR+/HER2- subgroup, respectively. The CPS+EG system distinguished different prognostic groups with 5-year DFS ranging from 0% to 91%. The CPS+EG system leads to an improved categorisation of patients by outcome compared to CS, PS, ER or NG alone. When applying the CPS+EG score to the HR+/HER2- subgroup, a shift to lower scores was observed compared to the overall population, but 5-year DFS and OS for the individual scores were identical to that observed in the overall population.
Conclusions: In HR+/HER2- patients, the CPS+EG staging system retains its ability to facilitate a refined stratification of patients according to outcome. It can help to select candidates for post-neoadjuvant clinical trials in luminal breast cancer.
Keywords: Breast cancer; CPS+EG score; HER2 negative; Hormone-receptor positive; Neoadjuvant chemotherapy; Pathologic complete response; Prognosis.
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