Maintenance treatment in metastatic breast cancer.

Metastatic breast cancer (MBC) occurs in 20-30% of women with breast cancer and is an incurable disease. Treatment is palliative and directed to prolong survival, decrease symptoms and improve patients' quality of life. For patients with hormone receptor-negative disease or for hormone receptor-positive disease that has become resistant to endocrine therapy, or is progressing rapidly and life threatening, cytotoxic chemotherapy is indicated. However, the optimal duration of chemotherapy treatment for MBC is still a matter of debate. Studies using maintenance chemotherapy regimens standard in the 1990s showed a consistent benefit with a more prolonged time to progression, although an improvement in survival was only demonstrated in one study. Two recent trials with newer cytotoxic agents showed controversial results; whereas one study concluded that the policy of prolonging treatment in chemotherapy-sensitive patients, after aggressive, modern combination chemotherapy, cannot be recommended for women with MBC, the other study showed that maintenance therapy with pegylated liposomal doxorubicin significantly prolonged time to progression in MBC patients after first-line chemotherapy without significant clinical toxicity. Initial data regarding metronomic chemotherapy indicate that continuously low-dose cyclophosphamide and methotrexate is minimally toxic and effective in heavily pretreated breast cancer patients. In daily practice, maintenance chemotherapy is a reasonable strategy that prolongs time to progression in patients with MBC who did not show progression after first-line chemotherapy. However, this benefit should be considered together with toxicities of treatment and the patient's preference.