Commercializing pharmacogenomics, or personalized medicine, seems to require carving up large markets and developing more treatments targeted at fewer patients. But Bristol-Myers Squibb Co. is betting that in cancer, the opposite may be true.

The pharma company last week jumped head-first into pharmacogenomics, where it believes that, at least in cancer, the science will uncover patient populations existing across several tumor types that respond to a single therapy. The idea is that the resulting patient populations will be as big as before.