CHICAGO, United States (AFP) — A major clinical trial using a new anti-cancer medicine cocktail by the Swiss pharmaceutical giant Roche produced only a modest gain in survival, researchers said Monday.

The study added pertuzumab (Perjeta) to the standard therapy, trastuzumab (Herceptin), in 4,805 women with HER2-positive breast cancer, an aggressive illness.“At an early follow-up of three years, 93.2 per cent of women who received trastuzumab alone had not developed invasive disease compared with 94.1 per cent of those who received pertuzumab and trastuzumab, a difference of one per cent,” said the report, released at the American Society for Clinical Oncology conference, the world’s largest gathering of cancer professionals.“Women with HER2-positive breast cancer used to have a worse prognosis than those with HER2-negative cancer, but the advent of HER2-targeted therapy changed the outlook for these women,” said lead study author Gunter von Minckwitz, president of the German Breast Group in Neu-Isenburg, Germany.“Our early findings suggest that we may be able to further improve outcomes for some women by adding a second HER2-targeted treatment without increasing risk for serious side effects.”Herceptin revolutionised breast cancer treatment after it was approved in 1998.It works by attaching itself to HER2 receptors on the surface of breast cancer cells and blocking them from receiving growth signals.Herceptin and Perjeta cost about US$70,000 each for one year of use. Together they bring in nine billion dollars a year for Roche.Between 15 and 25 per cent of all breast cancers are HER2-positive.“It is promising that some women in this study benefited more from treatment with two HER2-targeted therapies rather than one, but it is clear this approach may not be advantageous for women with a lower risk for recurrence.”