Three new breast cancer market entrants—Roche/Genentech’s Perjeta (pertuzumab) and trastuzumab-DM1 (T-DM1), and Novartis’s Afinitor (everolimus)—will drive growth in the breast cancer market through 2021, according to Decision Resources, a research and advisory firm for pharmaceutical and healthcare issues.

Having secured regulatory approval in both Europe and the U.S. for later-line hormone-receptor positive breast cancer in July, Decision Resources estimates that Afinitor’s major-market peak-year sales in this setting will exceed $1 billion. Furthermore, following the FDA’s approval of Perjeta in combination with trastuzumab and docetaxel (Sanofi’s Taxotere, generics) for first-line advanced HER2-positive breast cancer in June 2012, ongoing clinical development of the drug will enable it to secure blockbuster sales by 2021. T-DM1 has demonstrated impressive results in later-line treatment of HER2-positive breast cancer and Decision Resources anticipates the agent will be approved in this setting in 2013, and will move into earlier settings through 2021.

The Pharmacor breast cancer advisory service also found that, in 2011, Roche/Genentech/Chugai’s Herceptin (trastuzumab) earned $3.4 billion across the major markets, making it the highest-selling breast cancer drug in the U.S., France, Germany, Italy, Spain, the U.K. and Japan. However, during the 10-year forecast, the entry of biosimilar trastuzumab will erode sales of Herceptin.

The findings also reveal that major-market sales to treat breast cancer, which totaled $8.6 billion in 2011, will rise steadily to approximately $10.9 billion in 2018, before plateauing through 2021. Price erosion of key agents such as Herceptin will be offset by the uptake of novel premium-priced therapies, as well as an increase in the diagnosed incident breast cancer population as a result of population aging.

“Breast cancer drug development is a hive of activity but despite the busy pipeline, we forecast the uptake of just three novel agents in this market through 2021,” said Decision Resources analyst Amy Duval, M.Res. “Two of these agents will penetrate only the HER2-positive market segment, which will continue to be dominated by Roche. Although HER2-positive disease accounts for less than 25% of breast cancer cases, in 2011 it earned 55% of the breast cancer market and this is set to rise further to 65% in 2021.”

The Pharmacor patient flow model for breast cancer, which contains detailed methodology that includes the modeling of recurrent cases of breast cancer, finds that 62% of the first line drug-treatment opportunities per year for advanced disease—measured as the number of women per year that become eligible for first line drug-treatment for advanced disease—are the result of recurrent disease, rather than women first presenting with advanced disease. Due to the anticipated approval of novel agents that will improve outcomes for localized disease, Decision Resources forecasts that the number of women first presenting with advanced disease will grow at a faster rate than those with recurrent disease, thus reducing the proportion to 57% by 2021, and 54% by 2031.

In comparison with many other forms of cancer the prognosis for advanced breast cancer is good, with a mean life expectancy following development of advanced disease in 2011 (whether newly diagnosed or recurrent) projected to be over three years. If historical trends in survival continue, a further six months will be added to this figure in 2021, thus extending the duration of drug-treatable advanced disease by almost 20% over this 10-year period.