NEW YORK (Reuters Health) – In a phase III trial in women with HER2/hormone receptor-copositive metastatic breast cancer, the combination of trastuzumab plus anastrozole improved outcomes compared to anastrozole alone.
In the international TAnDEM study, 207 postmenopausal women with these tumor characteristics all took daily doses of anastrozole, and 103 of the subjects also received trastuzumab infusions every week until progression.
“Approximately 15% of patients who received trastuzumab plus anastrozole did not experience disease progression for at least 2 years,” the investigators report in the September 28th Journal of Clinical Oncology, “suggesting that the use of HER2-targeted therapy with an aromatase inhibitor can substantially delay chemotherapy in some patients who experience clinical benefit.”
According to Dr. Bella Kaufman from the Chaim Sheba Medical Center, Tel Hashomer, Israel and colleagues, median progression-free survival was significantly longer in the trastuzumab plus anastrozole arm (4.8 months) than in the anastrozole only arm (2.4 months). This translated into 2-year progression-free actuarial survival rates of 15% and 5%, respectively.
In both arms, “progression-free survival was shorter than might be expected,” probably because these tumors are so aggressive, the researchers admit.
Median overall survival (28.5 months versus 23.9 months, respectively) and 2-year actuarial survival rates (57% versus 50%, respectively) did not differ significantly between the study arms.
The investigators point out, however, that anastrozole-only patients who had disease progression were allowed to switch to a trastuzumab-containing protocol, which “may have reduced any overall survival benefit with trastuzumab plus anastrozole” in the intent-to-treat analysis “by improving overall survival in the anastrozole-only arm.”
Rates of clinical benefits and of partial responses were significantly higher in the trastuzumab plus anastrozole arm than in the anastrozole only arm, the researchers note, but no patient in either group achieved a complete response as assessed on the basis of World Health Organization standardized criteria.
Median duration of response and median time to response did not differ between the 2 treatment arms.
There were more grade 3 and grade 4 adverse events in the trastuzumab plus anastrozole arm, but “they were reversible, and none was life threatening,” according to the authors. More patients in the trastuzumab plus anastrozole arm discontinued treatment because of adverse events.
