23rd March, 2012
Chemotherapy drugs work better against cancer when combined with cycles of short, severe fasting, a study has found.
According to world-science.net, researchers suggest the fasting might help because normal cells tend to put off trying to divide when nutrients are lacking—but cancer cells keep trying, and this process ultimately kills them.
Fasting, even on its own, effectively treated a majority of cancers tested in mice, including transplanted cancer tumors made of human cells, researchers said. Their study, published in the journal Science Translational Medicine, found that five out of eight cancer types in mice responded to fasting alone: just as with chemotherapy, fasting slowed the growth and spread of tumors. And without exception, “the combination of fasting cycles plus chemotherapy was either more or much more effective than chemo alone,” said study senior author Valter Longo of the University of Southern California.
Multiple cycles of fasting combined with chemotherapy cured 20 percent of mice with a highly aggressive type of children’s cancer that had spread throughout the body, and 40 percent of mice with a more limited spread of the same cancer, the authors added. No mice survived in either case if treated only with chemotherapy.
“We don’t know whether in humans it’s effective,” said Longo, adding that it would take a clinical trial of several years to find out. Results from the first phase of a clinical trial with breast, urinary tract and ovarian cancer patients, conducted at the university, have been submitted for presentation at the next annual meeting of the American Society of Cancer Oncologists. But the first phase tests only the safety of a therapy, in this case whether patients can tolerate two-day fasts before and after chemotherapy.
Reported by www.world-science.net
Fasting isn’t safe for everyone, Longo warned. The clinical trial didn’t enroll patients who already had lost more than 10 percent of their normal weight or who had other risk factors, such as diabetes. Fasting also can cause a drop in blood pressure and headaches, which could make driving and other activities dangerous for some.
In a case report study with self-reported data published in the journal Aging in 2010, 10 cancer patients who tried fasting cycles perceived fewer side effects from chemotherapy.
In mice, the new study found that fasting cycles without chemotherapy could slow the growth of breast cancer as well as the cancers melanoma, glioma and human neuroblastoma. In several cases, the fasting cycles were as effective as chemotherapy, the researchers said. Fasting also extended survival in mice bearing a human ovarian cancer. In the case of melanoma, a deadly skin cancer, the cancer cells became resistant to fasting alone after a single round, but the single cycle of fasting was as effective as chemothera in reducing the spread of cancer to other organs.
For all cancers tested, fasting combined with chemotherapy improved survival, slowed tumor growth and/or limited the spread of tumors, the investigators reported.
As with any potential cancer treatment, fasting has its limits, Longo stressed. The growth of large tumor masses was reduced by multiple fasting and chemotherapy cycles, but cancer-free survival wasn’t achieved, the researchers said. Longo speculated that cells inside a large tumor may be protected somehow or that the variety of mutations in a large tumor may make it more adaptable.
But he noted that in most patients, oncologists have at least one chance to attack the cancer before it grows too large.
Longo and collaborators at the U.S. National Institute on Aging studied one type of breast cancer in detail to try to understand fasting’s effects. While normal cells deprived of nutrients enter a dormant state similar to hibernation, the researchers saw that the cancer cells tried to make new proteins and took other steps to keep growing and dividing. The result, Longo said, was a “cascade of events” that led to the creation of damaging molecules called free radicals. These broke down the cancer cells’ DNA and destroyed them.
“The cell is, in fact, committing cellular suicide. What we’re seeing is that the cancer cell tries to compensate for the lack of all these things missing in the blood after fasting. It may be trying to replace them, but it can’t,” Longo said.
The new study bookends research published in the journal Proceedings of the National Academy of Sciences in 2008. In that work, Longo’s team showed that fasting protected normal cells against chemotherapy, but didn’t address the effect on cancer cells. The study also focused only on a single cancer and chemotherapy drug. The new work extends those results by showing that fasting not only fails to protect cancer cells, but makes them more vulnerable, Longo said. He called the effect “different stress sensitization” to reflect the change in vulnerability between normal and cancerous cells.
Longo’s interest in fasting and cancer grew from years of studies on the beneficial effects of fasting in yeast and other organisms. He found 15 years ago that starved yeast cells enter a stress-resistant mode as they wait for better times. By contrast, he said, the mutations in cancer cells come at a cost, such as a loss in adaptability to diverse environments.
“A way to beat cancer cells may not be to try to find drugs that kill them specifically but to confuse them by generating extreme environments, such as fasting, that only normal cells can quickly respond to,” Longo said.