High genomic grade index associated with poor prognosis for lymph node-negative and estrogen receptor-positive breast cancers and with good response to chemotherapy.

BACKGROUND: The aim of the present study was to investigate the prognostic value of the genomic grade index for lymph node-negative and estrogen receptor (ER)-positive breast cancers of Japanese women treated with adjuvant hormonal therapy alone, as well as the relation between genomic grade index and pathological complete response (CR) to neoadjuvant chemotherapy.

METHODS: Genomic grade index was determined by DNA microarray (U133plus2.0; Affymetrix, Santa Clara, Calif) in tumor tissues obtained from lymph node-negative and ER-positive breast cancers (n = 105) treated with adjuvant hormonal therapy alone or in breast tumor biopsy specimens (n = 84, Mammotome) obtained before neoadjuvant chemotherapy (paclitaxel followed by 5-fluorouracil/epirubicin/cyclophosphomide) to investigate the prognostic and predictive values of genomic grade index.

RESULTS: Recurrence-free survival of patients with high genomic grade index tumors was significantly (P < .001) lower than that of patients with low genomic grade index tumors (55% vs 88%, 10 years after surgery). Multivariate analysis demonstrated that genomic grade index was the most important and significant predictive factor for disease recurrence (P = .013) independently of other prognostic factors, including tumor size, histological grade, progesterone receptor, human epidermal growth receptor 2, and Ki67. High genomic grade index tumors showed a significantly (P = .022) higher pathological CR rate for neoadjuvant chemotherapy than low genomic grade index tumors (31.9% [15 of 47] vs 10.8% [4 of 37]).

CONCLUSIONS: Genomic grade index is a powerful prognostic factor for lymph node-negative and ER-positive tumors treated with adjuvant hormonal therapy alone, and high genomic grade index tumors are more likely to respond to chemotherapy. Genomic grade index also appears to be very useful for decision making regarding the need for adjuvant chemotherapy for lymph node-negative and ER-positive breast cancers.