An European Organisation for Research and Treatment of Cancer phase I study of lapatinib and docetaxel as neoadjuvant treatment for Human Epidermal Growth Factor Receptor 2 (HER2) positive locally-advanced/inflammatory or large operable breast cancer

Background: Lapatinib is an effective anti-HER2 therapy in advanced breast cancer and docetaxel is one of the most active agents in breast cancer. Combining these agents in pre-treated patients with metastatic disease had previously proved challenging, so the primary objective of this study aimed to determine the maximum tolerated dose (MTD) in treatment-naive patients, by identifying acute dose-limiting toxicities (DLT) during cycle 1 in the first part of a phases 1-2 neoadjuvant European Organisation for Research and Treatment of Cancer (EORTC) trial. Patients and methods: Patients with large operable or locally-advanced HER2 positive breast cancer were treated with continuous lapatinib, and docetaxel every 21 days for 4 cycles. Dose levels (DLs) were: 1000/75, 1250/75, 1000/85, 1250/85, 1000/100 and 1250/100 (mg/day)/(mg/m(2)). Results: Twenty-one patients were included. Two DLTs occurred at dose level 5 (1000/100); one grade 4 neutropenia >= 7 days and one febrile neutropenia. A further 3 patients were therefore treated at the same dose with prophylactic granulocyte-colony stimulating factor (G-CSF), and 3 patients at dose level 6. No further DLTs were observed. Conclusions: Our recommended dose for phase II is lapatinib 1000 mg/day and docetaxel 100 mg/m(2) with G-CSF in HER2 positive non-metastatic breast cancer. The dose of lapatinib should have been 1250 mg/day but we were mindful of the high rate of treatment discontinuation in GeparQuinto with lapatinib 1250 mg/day combined with docetaxel. No grade 3-4 diarrhoea was observed. Pharmacodynamics analysis suggests that concomitant medications altering P-glycoprotein activity (in addition to lapatinib) can modify toxicity, including non-haematological toxicities. This needs verification in larger trials, where it may contribute to understanding the sources of variability in clinical toxicity and treatment discontinuation. (C) 2012 Elsevier Ltd. All rights reserved.