Fasting may reduce chemo side-effects -U.S. study
WASHINGTON (Reuters) - 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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