Impact of Immunohistological Subtypes on the Long-term Prognosis of Patients with Metastatic Breast Cancer

Purpose: Although improved long-term prognoses for patients with metastatic breast cancer (MBC) have been demonstrated, few reports address overall survival (OS) with sufficient follow-up. Furthermore, the relevance of immunohistological subtypes to OS in MBC has not been clarified.

Methods: We evaluated, retrospectively, the OS of patients who had been initiated on systemic therapy for MBC between 2000 and 2008.

Results: The subjects of this study were 527 patients with MBC treated by systemic therapy. The median survival time (MST) was 55.5 months. The MST for each immunohistological subtype was as follows: luminal, 59.9 months; luminal-HER2, not reached; triple-negative, 18.6 months; and HER2-enriched, 49.9 months. According to multivariate analysis, metastasis-free intervals of ≥2 years and treatment with anthracycline for MBC were predictive of better OS. The predictors of shorter OS included disease progression after first-line treatment for MBC, triple-negative, and all histological factors, except papillotubular carcinoma, with liver metastasis, and having three or more initial metastatic sites.

Conclusions: The prognosis of the patients with MBC in this series was better than that reported before 2000, which is probably attributable to the use of novel, improved pharmacological agents. For example, luminal-HER2 tumors can be treated using both aromatase inhibitors and trastuzumab. Because of the lower toxicities, it is now possible to administer these agents for longer periods, resulting in better prognoses.