More Precise Precision Medicine

Precision medicine for cancer treatment sounds promising – sample the tumor, analyze the genome for cancer-related mutations, and then select treatment according to the genetic profile of the disease. And although the procedures involved may be complex, the concept itself is relatively simple – or is it?

In an opinion piece in Trends in Cancer, Syn Kok Yeo and Jun-Lin Guan argue that the current approach to breast cancer isn’t good enough (1). Breast cancer tumors often exhibit a high degree of intratumoral heterogeneity – and so, they say, diagnostic professionals should be using single-cell technologies to truly personalize treatment.

“If you use a treatment that’s targeting one subtype, which kills one type of breast cancer, often the other kind will actually expand,” said Guan (2). “That defeats the purpose of treatment.” Instead, he and Yeo suggest that single-cell analysis could reveal different cell types within individual tumors, including populations of cancer stem cells capable of differentiating into many different tumor types. These are especially concerning because they aren’t genetically distinct, but can still give rise to tumor heterogeneity and thus to treatment resistance. The authors also highlight studies that suggest breast cancer cells may be able to interconvert between different subtypes, adding yet another layer of potential heterogeneity to a single tumor.

What can be done against this kind of dynamic heterogeneity? Fortunately, single-cell diagnostic technology is advancing rapidly. Yeo and Guan recommend adding such technologies to the laboratory’s existing breast cancer diagnostic workflow, so that pathologists can use a more complete understanding of any given tumor to guide treatment decisions. Of course, that too is easier said than done; there are a number of questions yet to be answered before clinical approaches catch up to research methods. But with more attention on the potential for dynamic heterogeneity, Yeo and Guan believe we could not only better understand breast cancer, but provide more customized care to patients with challenging tumors.