Drug Combination Significantly Improves Outcomes in Breast Cancer

Allison Gandey

October 12, 2006

October 12, 2006 (Istanbul) –- A new 2-drug combination appears to help clinicians simultaneously target the estrogen receptor and HER2-signaling pathways in postmenopausal women with metastatic breast cancer. Researchers have shown that adding anastrozole (Arimidex, AstraZeneca) to trastuzumab (Herceptin, Roche) can double progression-free survival and triple overall response. "We found that 53% more patients experienced clinical benefit with combination therapy," lead author Bella Kaufman, MD, from the Chaim Sheba Medical Center, in Ramat Gan, Israel, said at the 31st Congress of the European Society of Medical Oncology (ESMO).

Up to 15% of all metastatic breast cancers are positive for both estrogen receptor and HER2, Dr. Kaufman told reporters during a news briefing about her late-breaking trial. "Currently, the majority of these women are treated with chemotherapy and trastuzumab, but we thought it might be possible to achieve the same result without the toxicity of chemotherapy. Also, 20% of the estrogen-receptor–positive population is treated with hormonal therapy alone, and for them, the combination offers benefit."

The randomized, controlled, open-label, multicenter, phase 3 study known as TANDEM was warmly received at the meeting, with session discussant José Baselga, MD, from the Vall d'Hebron University Hospital, in Barcelona, Spain, congratulating the researchers. He called the investigators "brave" for treating patients without chemotherapy, and he suggested a shift in clinical practice may well be on the horizon.

Important Gains in Progression-Free Survival

Dr. Baselga said it appears that, for patients with metastatic breast cancer positive for both estrogen receptor and HER2 with disease that is progressing slowly and no prior treatment with aromatase inhibitors, this new combination therapy may be indicated. But he noted that patients with prior aromatase inhibitor use should remain on trastuzumab alone. And those with aggressive disease that is progressing rapidly should receive more traditional combinations of trastuzumab and chemotherapy.

Dr. Kaufman and her team had randomly assigned 208 postmenopausal women with breast cancer to 1 of 2 treatment groups. A total of 104 patients received anastrozole 1 mg daily, and another 103 patients were given anastrozole with a trastuzumab-loading dose of 4 mg/kg followed by 2 mg/kg once a week until disease progression. Women whose disease progressed on the single drug were given the option to switch to the combination therapy.

The investigators reported that women who took both drugs experienced significant improvements in the length of time it took for their disease to worsen. Progression-free survival was 4.8 months on average, compared with 2.4 months in the single-drug group. Overall survival was also prolonged — 28.5 months compared with 23.9 — but this difference was not statistically significant, the research team emphasized.

"Treatment with anastrozole and trastuzumab was manageable, with no new or unexpected adverse events," Dr. Kaufman told reporters. "Further analysis is ongoing to better understand this patient population."

ESMO 31st Congress: Abstract LBA2. Presented October 2, 2006.


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