New drug shows promise for HER2-positive metastatic breast cancer
MedWire News: A new type of targeted therapy for breast cancer has shown encouraging results in patients with human epidermal growth factor receptor (HER)2-positive metastatic disease, researchers report.
The drug, trastuzumab-DM1 (T-DM1), is a HER2-directed antibody-drug conjugate that combines the anti-HER2 properties of trastuzumab with targeted delivery of the antimicrotubule agent DM1, explained Edith Perez (Mayo Clinic, Jacksonville, Florida, USA) and colleagues
Previous single-arm phase II studies of T-DM1 have demonstrated its efficacy and favorable safety profile. Therefore, Perez and team set-up a randomized phase II study comparing the efficacy and safety of T-DM1 with that of tamoxifen plus docetaxel in 137 patients with HER2-positive metastatic breast cancer
The patients received either T-DM1 at 3.6 mg/kg intravenously (iv) every 3 weeks (n=67), or tamoxifen at 6 mg/kg iv (8 mg/kg in cycle 1) plus docetaxel at 75 or 100 mg/m2 iv on day 1 every 3 weeks (n=70). They were treated until disease progression or unacceptable toxicity.
The researchers report that after a median follow-up of approximately 6 months the objective response rate (ORR) was 48% in patients administered T-DM1, compared to 41% in the trastuzumab plus docetaxel group.
Importantly, the rates of clinically relevant adverse events were significantly lower in the T-DM1 arm, at 37.3%, compared with the traztuzumab plus docetaxel arm, at 75.0%.
"We are encouraged by the results," said Perez at the 35th European Society for Medical Oncology Congress in Milan, Italy.
"The study demonstrated that T-DM1 has very good anti-tumor activity as well as much lower toxicity when evaluated side by side with the older 'standard'," she added.
The researchers note that their findings represent a preliminary analysis. Progression-free survival data, 1-year overall survival rates, mature ORR, and duration of response data are expected in 2011, they say.
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By Laura Dean