(ChemotherapyAdvisor) – The targeted antibody/drug conjugate T-DM1 is as safe and effective in previously-treated patients diagnosed with HER2-positive metastatic breast cancer in settings “approximating clinical practice” as it was found to be in clinical trials, according to results from the multicenter expanded access T-PAS study, presented during the 2013 Breast Cancer Symposium held in San Francisco, CA.

T-DM1 is a targeted conjugate therapeutic containing trastuzumab and cytotoxic DM1.

“In this study that more closely reflects the real-world setting, the safety profile of T-DM1 was similar to that previously reported in conventional clinical trials, with no new safety signals,” reported Denise Aysel Yardley, MD, of the Sarah Cannon Research Institute in Nashville, TN, and coauthors. “In this pretreated population (median of seven prior therapies for HER2-positive metastatic breast cancer), significant activity was observed.”

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A total of 215 patients were enrolled during May 2010 through September 2011, and data obtained before July 31, 2012 was then analyzed. Participants had received “a median of seven prior systemic metastatic breast cancer therapies (range 1-23) with a median cumulative anthracycline dose of 240 mg/m2 (range, 6-2,645),” the coauthors reported.

At a median follow-up of 5.9 months (range, 0.1-25.3 months), median T-DM1 duration was 5.0 months (range, 0-23 months) with 15.8% of patients having received more than 18 cycles of treatment. The objective response rate (ORR) was 25.6%.

The most common adverse events of any grade were fatigue (50.7%), nausea (36.3%), and headache (24.2%). Common grade 3 or higher adverse events included thrombocytopenia (7.9%), fatigue (4.7%), increased aspartate aminotransferase (3.7%), and anemia (3.7%), the researchers reported. Cardiac dysfunction was reported in 3.7% of participants, half of whom suffered grade 3 or higher events leading to discontinuation of T-DM1 treatment.