Outdated assessment of treatment response makes good Cancer drugs look bad

Tumor shrinkage is not the only measure of a successful anti-cancer therapy. A University of Colorado Cancer Center article published in the journal Frontiers in Oncology describes a promising alternative: metabolic imaging. Tumors rush their metabolism to grow and proliferate. By recognizing a drug's ability to stop this energy overuse, doctors may be able to determine a patient's response to a new, targeted therapy far earlier and with far more precision than watching and waiting for a tumor to shrink.
"What we have been using for decades is called RECIST - it measures the dimensions of a tumor and it does a good job of showing a patient's response to chemotherapy and radiation. These therapies (called cytotoxic) kill cells and so if they are working, we see the tumor shrink," says Natalie Serkova, PhD, investigator at the University of Colorado Cancer Center and professor at the University of Colorado School of Medicine.
However, many modern targeted therapies do not immediately kill cancer cells. Instead, they interrupt a cancer cell's ability to grow and proliferate, often by immediate cessation of metabolic rates. Eventually these cells "interrupted" by targeted therapies die, but cell death and tumor shrinkage are not immediate, direct markers of a therapy's usefulness. Serkova points out that a recent article published in the Journal of Clinical Oncology shows that 15 percent of patients who are taken off clinical trials due to perceived lack of response to a trial medication aren't in fact non-responders - the drug may be working for these people in a way that is not captured by RECIST.
One possible solution is to image a tumor's metabolic rate, such as glucose uptake. "Cancer are gluttons for glucose," Eckhardt says, meaning that in order to drive their growth, cancers burn glucose at many times the rate of healthy cells. Drugs including anti-EGFR therapies stop cancer cells' ability to over-use glucose.
"These new therapies stop a cancer cell's glucose uptake within 24 hours after the first dose, but changes in tumor volume happen months later," Eckhardt says. Is the drug working? Watching for changes in a tumor's use of glucose could answer this question months earlier than current RECIST criteria.