Roche ($RHHBY) breast cancer drug Herceptin has been so effective that it earns the Swiss drugmaker boatloads of money. And Roche today tightened its lock on the breast cancer treatment market, and its expectations for many more billions of dollars in annual revenue, when an EU panel gave thumbs up for approval of its companion drug Perjeta.

           A European Medicines Agency panel recommended the use of pertuzumab, now branded Perjeta, for HER2-positive disease, used in conjunction with other drugs. As Reuters points out, the European Commission usually accepts the recommendations within a couple of months. The FDA approved Perjeta in June.

           This new targeted breast cancer drug from Roche's Genentech unit is designed for use in tandem with the older Herceptin. A study released in June found that women with HER2-positive metastatic breast cancer lived significantly longer when treated with the combination of Perjeta and Herceptin, along with docetaxel chemotherapy, compared with Herceptin and docetaxel chemotherapy alone. Thus, Roche doesn't face having its newer drug cannibalize sales from Herceptin, which is forecast to earn $6 billion this year. Forecasts put Perjeta sales at $600 million to $2.5 billion for now and as high as a stratospheric $8.5 billion if it gets approved for a couple of other indications.

            Like other targeted cancer drugs, Perjeta is pricey. An 18-month treatment will run about $188,000, Reuters reports. But breast cancer is the most prevalent form of cancer globally for women, with 1.4 million cases diagnosed each year, and about 450,000 deaths, Reuters said, citing World Health Organization stats.