Tuesday, April 1, 2008

Fasting may reduce chemo side-effects

A few days of fasting might help protect patients from some of the unpleasant and dangerous side-effects of cancer chemotherapy, researchers reported on Tuesday.

They said mice given a high dose of chemotherapy after fasting thrived while half of a group of well-fed mice died, they reported in the Proceedings of the National Academy of Sciences.

The researchers stressed that people should not try this on their own yet but said the findings might lead to a way to use chemotherapy to more effectively kill tumors while sparing healthy cells.

Valter Longo of the University of Southern California and colleagues first tested yeast cells, then human cells in lab dishes. They found healthy cells starved of nutrients survived the ravages of chemotherapy -- but not cancer cells.

"In theory, it opens up new treatment approaches that will allow higher doses of chemotherapy. It's a direction that's worth pursuing in clinical trials in humans," cancer researcher Pinchas Cohen of the University of California, Los Angeles, who was not involved in the study, said in a statement.

Longo and colleagues said animals fed a low-calorie diet live longer, in part because their cells can resist stress better. They also noticed that starved cells go into a kind of hibernation mode, while cancer cells form tumors because they lack an "off" position, growing uncontrollably.

Longo wondered if the starvation response might be a way to differentiate healthy cells from cancer cells. One reason chemotherapy causes side-effects is that it affects all active and growing cells -- tumors, but also hair follicles, the lining of the intestines and other cells.

"Here, we tested the hypothesis that short-term starvation or low glucose/low serum can protect mammalian cells but not or to a lesser extent cancer cells, against high doses of oxidative damage or chemotherapy," they wrote.

"We administered an unusually high dose of etoposide (80 mg/kg) to ... mice that had been starved for 48 hours. In humans, one-third of this concentration of etoposide is considered to be a high dose and therefore in the maximum allowable range," they wrote.

The high dose killed 43 percent of the mice that were fed normally but just one starved mouse. The starved mice regained their lost weight within four days.

An even higher dose killed all of the well-fed mice from a different genetic strain but none of the starved mice, and again the mice that fasted regained their weight.

Other cancer experts said a few days of fasting would not harm most cancer patients.

"This could have applicability in maybe a majority of patients," said Dr. David Quinn of the University of Southern California.

"We have passed the stage where patients arrive at the clinic in an emaciated state. Not eating for two days is not the end of the world," agreed Felipe Sierra, director of the Biology of Aging Program at the National Institute on Aging.


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