this may be old news to folks - i tune in so rarely i am a little out of touch, i am sure - but it appears that there are different types of mutations that cause different types of breast cancer - one mutation, HER2, which results in a particularly aggressive cancer, is responsible for 25% of breast cancer cases, and a drug, herceptin, has been developed to treat HER2 cancer specifically. in clinical trials, women treated with herceptin for one year had - depending on what other therapies they also had - a 33-52% lower rate of recurrence.

so, it is possible that what we call a single disease can arise from multiple sources, and it is possible to identify and treat some - and, in theory, eventually all - of those sources.

i believe this is where interest in pd subtypes comes from, in addition to the search for genetic clues.