A simple system for grading the response of breast cancer to neoadjuvant chemotherapy

Background: The response of primary breast cancer to chemotherapy is usually expressed either as a pathological complete remission (pCR) or as 'no pCR'. A more quantitative measure is called for. Patients and methods: The 'neoadjuvant response index' (NRI) was calculated by adding a breast response score (a number from a five-point scale) to an axillary response score (a number from a three-point scale) and dividing this by the score that would have been obtained in case of a pCR in both breast and axilla. Consequently, the NRI is a number between 0 (representing no response) and 1 (a pCR of both breast and axilla). Results: The NRI was calculated in 267 patients who had received neoadjuvant chemotherapy. The average NRI was 0.48 (median 0.40). Forty-one patients (15%) had an NRI of 0; 55 patients (21%) had an NRI of 1 (pCR). 'Highly endocrine responsive' tumors responded substantially less than 'incompletely endocrine responsive' ones. In triple negatives, an NRI of >0.70 was associated with a better recurrence-free survival than a lower NRI. Conclusions: The NRI proposed here may be useful to better reflect the efficacy of neoadjuvant systemic regimens than the binary pCR-'no pCR' system.