NEW YORK (Reuters Health) Jul 02 - In HER2-positive early-stage breast cancer, six months of adjuvant trastuzumab is not equivalent to the standard 12 month course, according to French researchers.
"After 3.5 years follow-up, we failed to show that six months of treatment with trastuzumab was non-inferior to 12 months of trastuzumab," they said in a June 11th online paper in The Lancet Oncology. "Despite the higher rates of cardiac events, 12 months of adjuvant trastuzumab should remain the standard of care."
The authors, led by Dr. Xavier Pivot of University Hospital J Minjoz, Besancon, note that a shorter course has been advocated to alleviate cardiac concerns.
The new study was an open-label trial involving more than 3300 patients who received at least four cycles of chemotherapy, breast-axillary surgery, and up to six months of trastuzumab. They were randomly assigned to stop trastuzumab or continue it for another six months.
With follow-up lasting a median 42.5 months, intention-to-treat analysis showed two-year disease-free survival rates of 93.8% in the 12-month group and 91.1% in the six-month group (p for noninferiority = 0.29).
The 626 patients with estrogen-receptor-negative tumors treated with sequential chemotherapy and trastuzumab had the poorest disease-free survival: 89.8% in the 12-month group and 84.5% in the six-month group.
Overall, 159 patients (4.7%) died: 66 (3.9%) in the 12-month group and 93 (5.5%) in the six-month group. About this, the authors write, "The estimated hazard ratio was 1.46 (95% CI 1.06-2.01), however the test of proportional hazards was significant (p=0.03), indicating that proportional hazards cannot reasonably be accepted as plausible for overall survival."
"Longer follow-up with more events is required to provide mature data for overall survival," the researchers say.
There were 128 cardiac events (either clinical or based on assessment of left ventricular ejection fraction) while patients were receiving trastuzumab. These were significantly more common in the 12-month group than in 6-month patients (5.7% vs 1.9%).
The researchers note that a number of other trials are investigating shorter trastuzumab duration but "on the basis of the results presented here, 12 months of adjuvant trastuzumab should remain the standard of care for women with HER2-positive early breast cancer."
Commenting on the findings by email, Dr. Filippo Montemurro, co-author of an editorial published with the report, told Reuters Health, "Although the results of (this study) must not alter current clinical practice, they support the notion that the treatment of patients with HER2-positive operable breast cancer requires more individualized approaches."
In this respect, Dr. Montemurro of the Institute for Cancer Research and Treatment, Candiolo, Italy concluded that "trastuzumab treatment duration remains a potential component of tailored strategies."
Dr. Pivot did not respond to requests for comments.
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Lancet Oncol 2013.
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