0602 GMT - News that U.S. regulators approved AstraZeneca's new breast cancer drug Etcamah represents a minor positive for the U.K. pharmaceutical company, J.P. Morgan analysts say in a research note. The drug was approved for use in combination with medicines like Pfizer's Ibrance, Eli Lilly's Verzenio and Novartis's Kisqali to treat a type of breast cancer upon detection of a specific mutation. The authorization opens up a $1 billion sales opportunity for Etcamah, which reduces risk for one third of the consensus peak-sales estimate of $3 billion for the product, according to JPM. That said, the initial rollout of Etcamah could be slow due to the need to establish a new treatment paradigm of regular circulating tumor DNA testing to detect the mutation and a warning for arrhythmia risk, the analysts add.