The pharmaceutical company says that the late-stage, or Phase III, trial results are applicable to patients whose advanced breast cancer was hormone receptor-positive, as well as HER2-positive, which is a particularly aggressive form of the disease.
The company says that hormone receptor-positive breast cancer which affects two-thirds of patients with breast cancer is typically considered lower-risk due to successful treatment with hormonal therapies; but as many as a quarter of such breast cancers are also HER2-positive, an aggressive form of the disease that requires immediate attention because the tumors are fast-growing and there is a higher likelihood of relapse.
In the study the high profile, blockbuster drug Herceptin plus the hormone therapy Arimidex was compared with Arimidex alone as a first-line therapy or second line hormonal therapy in postmenopausal women with advanced, HER2-positive and hormone receptor-positive breast cancer.
Roche says patients who received Herceptin had a statistically significant improvement in progression-free survival.
At present Herceptin is only licensed in the European Union as a treatment for metastatic cancer a late-stage condition where tumors have spread around the body. European experts have backed the early use of the drug and the new approval would extend its use to a large number of, in the main, younger patients.
The injectable medicine is appropriate for 20 to 30 percent of women with a form of breast cancer whose tumors generate a protein called HER2, making them particularly fast-growing.
The study is the first randomised study in this specific subset of 'co-positive' patients, whose prognosis has been uncertain thus far.
The researchers found that among the women in the first group, the 10-year risk of breast cancer returning was 12.1%; among the group who received 39 grays it was 14.8%, but among those who got the slightly higher dose of 42.9 grays it was 9.6%.
Lead researcher Professor John Yarnold suggests it should be possible to give fewer but higher daily doses of radiotherapy to the breast to prevent cancer from returning without harming the patient's healthy tissues.
Professor Yarnold says the results of further trials that have followed this study will need to be evaluated before they can confirm that the strategy is more effective than the standard treatment in the long term.
Experts have welcomed the findings and say the trial is important.
They say if confirmed it could mean better outcomes with less hospital visits and anything that improves a patient's experience of breast cancer treatment and is as effective as the current standard, with no increase in side effects, is to be welcomed.
The study is published in the current issue of the Lancet.