'Personalized Medicine' Hits a Bump
Wall Street Journal -
Tumor Evolution More Complex than Imagined
Personalized cancer treatment: Genetic differences abound in tumors Los Angeles Times
The source of this pessimism? A study in the NEJM: Intratumor Heterogeneity and Branched Evolution Revealed by Multiregion Sequencing
Here's Ron Winslow of the WSJ passing sentence on why the study is a blog to targeting treatments:
"Tumor's genetic makeup can vary significantly even within the same tumor sample, researchers said, a finding that poses new challenges to the personalized-medicine movement in cancer.
One big implication of the new research, being published Thursday in the New England Journal of Medicine, is that analyzing only a single sample of a patient's tumor—the current practice—may miss important genetic mutations that affect the course of the disease.That, in turn, could hinder emerging efforts to match patients with drugs that target the mutations affecting their tumors, a basic strategy of personalized medicine.
The findings don't diminish enthusiasm for the idea that genetic knowledge about tumors can transform cancer care, the researchers said. But it could make personalized treatment more complex—and more costly."
Winslow and others -- following the bias of the researchers who did the study -- overstate the novelty of finding differences in tumor progression because of differences in mutations identified by exome sequencing and appear to suggest that such subtle changes always mislead.
First, exome sequencing is becoming commonplace, as is deep sequencing of the type provided by Life Technologies and Oxford Nanopore Technologies. The costs and speed of such analysis is dropping rapidly. So cost is not a factor. Second, such sequencing will become commonplace precisely because clinicians know that every cancer progresses differently. Mutations are not always associated with changes in tumor progression. Sometimes they are, sometimes they are not.
Winslow and others present personalized medicine as a single gene-single step process of individualizing treatment. No one who knows anything about the clinical and functional application of sequencing believes that. Hence, the media -- where many 'thought leaders' still get the primary source material on health and science -- perpetuates both an outdated view of personalized medicine and artificially overstates the costs and barriers of the same.