Costing between $36,000 (€30,000) to $47,000 a year for each patient, Herceptin is already licensed in Europe and in the US as treatment for metastatic advanced cancer, with 230,000 patients using it worldwide.
But the expansion of the drug's scope to mainly younger women with less advanced disease would significantly boost Roche's sales for Herceptin, which totalled $1.64 billion last year, up 48 per cent on 2004, making the product the firm's third biggest seller.
The European application is based on data from the international HERA (HERceptin Adjuvant) study, involving nearly 12,000 patients, which showed that Herceptin, following standard chemotherapy, reduces the risk of cancer coming back by 46 per cent.
These results have emboldened campaigners in countries who want the drug included in their national health systems for early stage HER2 breast cancer.
The issue attracted plenty of headlines in the UK last week when a woman diagnosed with aggressive HER2 form of breast cancer lost her legal challenge over her local National Health Service (NHS) trust's refusal to fund treatment with Herceptin.
Liz Caroll, head of clinical services at British charity Breast Cancer Care, told In-Pharmatechnologist.com the drug would make a significant but not dramatic contribution to breast cancer treatment.
"In the HERA study, if you follow up the benefits of the drug for a year, Herceptin increased the number of HER2-positive women who were disease-free by 6 per cent," she said.
"Now that is a notable difference compared to other treatments but it is not a drug that will suit anybody with breast cancer."
The injectable medicine is suitable for 20 to 30 per cent women with a particularly aggressive form of breast cancer whose tumours produce a potentially carcinogenic protein called HER2.
Eight to nine per cent of women will develop breast cancer during their lifetime, making it one of the most common types of cancer in women.
"The clinical trials show Herceptin has had an important impact in the fight against HER2-positive breast cancer," Roche spokeswoman Martina Rupp told In-Pharmatechnologist.com.
"If you find this to be an expensive drug you have to looks at its benefits and the increase in survival rates.
Herceptin is a humanised antibody, designed to target and block the function of HER2, and has not only showed efficacy in the early-stage breast cancer setting, but has also demonstrated improved survival in the advanced setting, where its addition to chemotherapy allows patients to live up to one-third longer than chemotherapy alone.
Currently Herceptin is indicated for use in combination with docetaxel as a first-line therapy in HER2-positive patients who have not received chemotherapy for their metastatic disease, as a first-line therapy in combination with paclitaxel where anthracyclines are unsuitable, and as a single agent in third-line therapy.