Lapatinib: the evidence for its therapeutic value in metastatic breast cancer

INTRODUCTION: Breast cancer is the most common cancer affecting women. Many patients ultimately progress to metastatic disease and optimal management of this disease remains a significant therapeutic challenge. Lapatinib, a dual tyrosine kinase inhibitor, is in clinical development for treatment of this disease. AIMS: The objective of this article is to review the published evidence for the treatment of metastatic breast cancer with lapatinib, and assess its therapeutic potential. EVIDENCE REVIEW: Most evidence has appeared in meeting abstract reports of phase I and II studies in healthy volunteers and cancer patients. Four studies have included patients with exclusively breast cancer. Complete and partial responses and stable disease has been reported in some patients. Emerging evidence indicates that complete and partial responses can be achieved in some patients with metastatic breast cancer. Lapatinib appears to be well tolerated in cancer patients and the maximum tolerated dose is in the region of 1800 mg/day. In addition, it has been used in combination with other cancer treatments. Five ongoing or planned phase II monotherapy and three phase III combination-therapy studies with lapatinib have been identified. OUTCOMES SUMMARY: The phase I and II studies reported to date have provided safety data and preliminary indications regarding efficacy. There is preliminary evidence that lapatinib can achieve objective response rates of 10–38% in patients with metastatic breast cancer. Patients with tumors overexpressing ErbB1 and/or ErbB2 are likely to benefit from lapatinib treatment.