Lapatinib plus Capecitabine versus Trastuzumab plus Capecitabine in the Treatment of Human Epidermal Growth Factor Receptor 2-positive Metastatic Breast Cancer with Central Nervous System Metastases for Patients Currently or Previously Treated with Trastuzumab (LANTERN): a Phase II Randomised Trial

Aims: Brain (central nervous system; CNS) metastases occur in 30-50% of patients with human epidermal growth factor receptor 2 (HER2)-positive metastatic breast cancer (MBC). A substantive evidence base for treatment is lacking, but activity with lapatinib plus capecitabine (lap-cap) has been reported. We compared lap-cap with trastuzumab plus capecitabine (tras-cap) in patients with HER2-positive MBC with CNS metastases previously treated with trastuzumab.

Materials and methods: This open-label randomised phase II screening trial aimed to randomise 130 participants over 2 years to receive lap-cap or tras-cap. Eligible patients had HER2-positive MBC with newly diagnosed or recently progressed CNS metastases; previous, or current, treatment included: trastuzumab, a taxane or anthracycline and recent completion of local cranial therapy. The primary end point was time to progression of CNS metastases within the 24-week trial period. Secondary objectives included CNS response rate, progression-free survival, steroid use for CNS symptoms and feasibility of recruitment to a large phase III trial.

Results: Between September 2011 and October 2013, 30 participants were randomised, 16 to lap-cap and 14 to tras-cap. Recruitment to a large phase III trial was determined not to be feasible. At 24 weeks, CNS disease progression was 41.8% (95% confidence interval 16.1-67.5%) in lap-cap and 41.2% (95% confidence interval 12.8-69.6%) in tras-cap arms; progression-free survival was 44.4% (95% confidence interval 18.1-70.8%) in lap-cap and 50.0% (95% confidence interval 20.9-79.1%) in tras-cap arms.

Conclusion: Poor recruitment confirmed that a larger phase III trial would not be feasible and prohibited a preliminary evaluation of the superiority of lap-cap over tras-cap. Descriptive statistics are presented to inform the limited evidence base and future study design.