ABSTRACT
BACKGROUND: A recurrence score based on a 21-gene expression assay predicts the benefit of adjuvant chemotherapy in oestrogen receptor (ER)-positive, human epidermal growth factor receptor 2 (HER2)-negative breast cancer. This systematic review aimed to determine whether the 21-gene expression assay performed on core biopsy at diagnosis predicted pathological complete response (pCR) to neoadjuvant chemotherapy. METHODS: The study was performed according to PRISMA guidelines. Relevant databases were searched to identify studies assessing the value of the 21-gene expression assay recurrence score in predicting response to neoadjuvant chemotherapy in patients with breast cancer. The Newcastle-Ottawa Scale was used to assess the quality of the studies. Results are reported as risk ratio (RR) with 95 per cent confidence interval using the Cochrane-Mantel-Haenszel method for meta-analysis. Sensitivity analyses were carried out where appropriate. RESULTS: Seven studies involving 1744 patients reported the correlation between pretreatment recurrence score and pCR. Of these, 777 patients (44.6 per cent) had a high recurrence score and 967 (55.4 per cent) a low-intermediate score. A pCR was achieved in 94 patients (5.4 per cent). The pCR rate was significantly higher in the group with a high recurrence score than in the group with a low-intermediate score (10.9 versus 1.1 per cent; RR 4.47, 95 per cent c.i. 2.76 to 7.21; P < 0.001). A significant risk difference was observed between the two groups (risk difference 0.10, 0.04 to 0.15; P = 0.001). CONCLUSION: A high recurrence score is associated with higher pCR rates and a low-intermediate recurrence score may indicate chemoresistance. Routine assessment of recurrence score by the 21-gene expression assay on core biopsy might be of value when considering neoadjuvant chemotherapy in patients with ER-positive, HER2-negative breast cancer.