Not all cells within a tumor are cancer cells, and those healthy cells that have fallen in with malignant ones alter the properties of the tumor, affecting how it reacts to certain treatments, NPR reports.
In Nature Communications, University of California, San Francisco's Atul Butte and his colleagues report that they assessed tumor purity of more than 10,000 tumor samples from across 21 cancer types from the Cancer Genome Atlas.
"Cancers actually have a lot of different types of cells in them, including immune cells or inflammatory cells," Butte tells NPR.
And this composition influences survival. Butte adds that tumor purity "had a lot to do with whether or not that patient ended up surviving that cancer and whether a particular drug seemed to be effective or not."
What immune cells are present may be a key trait, Reena Thomas, a neuro-oncologist at Stanford Health Care who was not involved in the study, tells NPR. These cells, she says, could make patients' tumors more susceptible to immunotherapies. "That gives us a clue as to knowing why some patients like President Carter might respond to this therapy, but it could be by cancer and it could be by patient," she adds.
Butte adds that the only way to be sure is to sample multiple parts of each tumor. "More detailed measurements of cancers, biology, and DNA are increasingly important for us to reach this precision medicine targeting the right drugs," he says. "We need better tools and models, but the data and the measurements are going to get us there."