anastrozole + capecitabine

The combination of anastrozole and capecitabine is used in the treatment of hormone receptor-positive metastatic breast cancer. This combination therapy has shown promising results in both first-line and second-line treatment settings. ## Pharmacological Information **Mechanism of Action** Anastrozole is an aromatase inhibitor (AI) that works by blocking the enzyme aromatase, which is responsible for converting androgens into estrogens. This reduces estrogen levels in the body, which can slow or stop the growth of hormone-sensitive breast cancer cells[1]. Capecitabine is an oral fluoropyrimidine carbamate that functions as a prodrug. It has little pharmacological activity until it's converted to 5-fluorouracil (5-FU) by enzymes that are expressed in higher concentrations in many tumors. This targeted conversion allows for more selective delivery of the active compound to tumor tissues[7]. Preclinical studies have shown synergistic activity between these agents. The combination enhances antitumor efficacy in estrogen receptor (ER)-positive cell lines[1]. Metronomic chemotherapy (like capecitabine) upregulates genes associated with the ER signaling pathway and downregulates proliferation-related genes, thus enhancing tumor cell susceptibility to endocrine therapy[3]. **Dosing** In clinical studies, the combination regimen typically consists of: - Capecitabine: 500 mg three times daily continuously[3] or 650 mg/m² twice daily for 14 days in a 21-day cycle[5] - Anastrozole: 1 mg daily[3][5] ## Clinical Efficacy The combination of anastrozole and capecitabine has demonstrated improved progression-free survival (PFS) compared to either agent alone: - As first-line treatment: PFS of 21 months for the combination vs. 8.0 months for capecitabine alone and 15.0 months for AI alone[1][5] - As second-line treatment: PFS of 18 months for the combination vs. 5.0 months for capecitabine alone and 11.0 months for AI alone[1][5] Several phase II trials have reported median PFS ranging from 10 to 17 months and objective response rates from 31.8% to 70.5% for metronomic capecitabine plus an AI, with one study notably demonstrating a median PFS of 20.9 months in first-line therapy patients[3]. ## Safety Profile The combination treatment has been reported to be safe with lower toxicity compared to conventional dosing regimens[1]. Common adverse events include: - Hand-foot syndrome (69%, mostly grade 1-2) - Fatigue (64%, mostly grade 1) - Diarrhea (29%, mostly grade 1) - Grade 3 hand-foot syndrome (reported in a small percentage of patients)[1][5] The risk or severity of cardiotoxicity can be increased when capecitabine is combined with anastrozole[7]. ## Current Development Status The combination is being studied in various clinical settings for hormone receptor-positive, HER2-negative breast cancer. While showing promising results in retrospective analyses and phase II studies, prospective randomized clinical trials are needed to confirm these findings[1][4]. This combination approach represents a potential treatment option for patients with hormone receptor-positive metastatic breast cancer, particularly in the post-CDK4/6 inhibitor setting[3].