Fasting slows cancer growth in mice

Washington -  A new study has found that fasting is as effective as chemotherapy in reducing the growth and spread of cancers in mice.

The study also found that chemotherapy drugs work better when combined with cycles of short, severe fasting.

And without exception, “the combination of fasting cycles plus chemotherapy was either more or much more effective than chemo alone,” said senior author Valter Longo, professor of  gerontology and biological sciences at the University of Southern California.

For example, 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 organism and  40 percent of mice with a more limited spread of the same cancer.

No mice survived in either case if treated only with chemotherapy.

The first phase of a clinical trial conducted at the USC Norris Comprehensive Cancer Center and led by oncologists Tanya Dorff and David Quinn, in collaboration with Longo tests only the  safety of a therapy, in this case whether patients can tolerate short-term fasts of two days before and one day after chemotherapy.

In mice, the study found that fasting cycles without chemotherapy could slow the growth of breast cancer, melanoma, glioma and human neuroblastoma. In several cases, the fasting cycles were as effective as chemotherapy.

Fasting also extended survival in mice bearing a human ovarian cancer. In the case of melanoma, the cancer cells became resistant to fasting alone after a single round, but the single cycle  of fasting was as effective as chemotherapy 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.

As with any potential cancer treatment, fasting has its limits. The growth of large tumor masses was reduced by multiple fasting and chemotherapy cycles, but cancer-free survival could not  be achieved.

Longo speculated that cells inside a large tumor may be protected in some way or that the variety of mutations in a large mass may make it more adaptable.

Only a clinical trial lasting several years can demonstrate whether humans would benefit from the same treatment, Longo cautioned.

The study appeared in Science Translational Medicine, part of the Science family of journals.