If you’re overweight, your chances of surviving cancer are far less than if you were of normal weight, studies point out. But it isn’t the number on the scale that affects the chances of survival. It all has to do with the fact that doctors aren’t basing the size of chemotherapy doses on the patient’s weight…and they should be, says a panel of oncologists.

The largest organization of doctors who treat cancer, the American Society of Clinical Oncology, aims to address this fatal error and is offering new guidelines suggesting weight-based doses for obese patients suffering from all forms of cancer.

Even receiving a little less chemotherapy than necessary can severely decrease one’s chance of survival, reports an article in the Washington Post. Alarmingly, various studies have shown that as many as 40 percent of obese cancer patients have been getting less than 85 percent of the right dose for someone their size.

It’s time for that to change, says Dr. Gary Lyman, a Duke University oncologist who led the panel that wrote the new guidelines.

“Don’t call it super-sizing; it’s right-sizing cancer care,” Lyman says. “There’s little doubt that some degree of undertreatment is contributing to the higher mortality and recurrence rates in obese patients.”

Dr. Richard Pazdur, head of the FDA’s cancer drug department, heartily agrees with the panel’s advice.

“By minimizing the dose, or capping the dose, we have been undertreating patients,” he said.

Experts say the dosing applies to all types of cancer normally treated with chemotherapy including breast, colon, ovarian, and lung cancers as well as leukemia and other blood diseases. Mesothelioma patients receiving Alimta or other chemo drugs could be in the same proverbial boat.

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.

The panel notes that while big certainly isn’t healthy, it’s tending to be the new norm in America, with 60 percent of all Americans considered overweight and some 35 percent falling into the obese category. That’s why this study is so essential.

In addition, similar studies actually show that overweight patients are less likely to develop dangerous, low blood counts from cancer treatment, and that they are able to more quickly clear chemo drugs from their body.