Breast cancer isn't breast cancer. Or rather it isn't a single disease. It's a whole collection of different problems that are collected under one heading because they all originate in the same place. Oncologists have known this for some time, I'm not sure the general populace knows. The cool bit is that, now with quick and comparatively cheap genome sequencing, it's beginning to be possible to differentiate between which set of problems an individual patient may have. Which means that treatments can be targeted a lot better than they have been in the past. A research group in Missouri have just finished sequencing the genomes from the tumors of 50 breast cancer patients. There's a quote there which is apt: "The more we learn about breast cancer, the more complicated it becomes. The amount of genomic variation was quite large. Of all the 1700 mutations found only 3 were common to 10% of the patients, most of the mutations were patient specific. There were a few genes identified that were commonly (though not universally) broken. All of which gives one hope. As we find out more, it becomes more complex, but as it becomes more complex, we understand it better.