Cancer doctors aim to 'right-size' chemo for obese patients

By

Published:

 

Obese people are less likely to survive cancer, and one reason may be a surprising inequality: The overweight are undertreated.

Doctors often short them on chemotherapy by not basing the dose on size, as they should. They use ideal weight or cap the dose out of fear about how much treatment an obese patient can bear. Yet research shows that bigger people handle chemo better than smaller people do.

Even a little less chemo can mean worse odds of survival, and studies suggest that as many as 40 percent of obese cancer patients have been getting less than 85 percent of the right dose for their size.

Now, the largest organization of doctors who treat cancer, the American Society of Clinical Oncology, aims to change that. The group has adopted guidelines urging full, weight-based doses for the obese.

Don't call it supersizing; it's right-sizing cancer care, said Dr. Gary Lyman, a Duke University oncologist who led the panel that wrote the advice.

"There's little doubt that some degree of undertreatment is contributing to the higher mortality and recurrence rates in obese patients," he said.

The Food and Drug Administration's cancer drug chief, Dr. Richard Pazdur, agrees.

The dosing issue applies to all types of cancer treated with chemo — breast, colon, lung, ovarian and even blood diseases such as leukemia.

It affects a lot of people. Big isn't healthy but it's the new "normal" — 60 percent of Americans are overweight and more than one-third of them are obese.

Giving too little chemo "could make it as if they didn't even get treated at all … so they go through the whole ordeal with no benefit, in the extreme case," said Dr. Jennifer Griggs, a University of Michigan breast cancer specialist who also worked on the guidelines.

So why do doctors limit dose?

Sometimes it's for good reason — the patient has diabetes, heart problems or other illnesses that interfere with how much chemo they can stand. Usually, though, it's because doctors are afraid to follow a standard weight-based formula because the dose seems so huge and they're afraid of harming the heart and blood system, Lyman said.

Yet studies show that heavier patients are less likely to develop dangerous, low blood counts from cancer treatment, and that they clear chemo drugs more quickly from the body than thinner people do.

A paper Lyman published in the journal Nature in August said that a 20 percent reduction in chemo doses lowered remission and cure rates by half in animal experiments and helped the tumors develop resistance to the drugs. Other research in people found lower survival among those getting less chemo as well.