Abstract
The identification of women with early-stage breast cancer who will develop distant metastasis may improve clinical management. The transcriptional regulator Enhancer of Zeste-2 (EZH2) is overexpressed in invasive breast carcinoma compared with benign breast tissues, with maximal expression in breast cancer metastasis. In this article, our purpose was to investigate the performance of EZH2 protein detection as a predictor of metastasis in women with early-stage breast cancer, which is unknown. We developed a cohort of 480 women with stage I-IIA breast cancer diagnosed between 1996 and 2002 and recorded detailed sociodemographic, clinical, and pathological information. Tumors were histologically characterized and arrayed in tissue microarrays containing 1,443 samples. The nuclear EZH2 expression was investigated by immunohistochemistry and was scored as 1-2 (negative and weak) or 3-4 (moderate and strong) using a validated scoring schema. Scores 1-2 were considered low EZH2; scores 3-4 were considered high EZH2. In this study, we found that after a median follow up of 9 years (range 0.04-14.5 years) 46 of 480 patients (9.6%) developed distant metastasis. High EZH2 was associated with larger size, high histological grade, negative hormone receptors, and first degree family history of breast and/or ovarian carcinoma. While EZH2 could not predict survival in the entire cohort, high EZH2 was a predictor of disease-specific survival in patients with early-stage disease and first degree family history (log rank P value 0.05). Importantly, in this group of patients, high EZH2 was an independent predictor of distant metastasis up to 15 years after primary carcinoma diagnosis (hazard ratio 6.58, 95% CI: 1.40-30.89, P = 0.016) providing survival information above and beyond currently used prognosticators. In conclusion, EZH2 may be a useful biomarker of long-term metastatic risk in women with familial early-stage breast cancer, and warrant further validation studies.