Soy Isoflavones Enhance Lung Cancer Radiation Treatment

DETROITCompounds found in soybeans can make radiation treatment of lung cancer tumors more effective while helping to preserve normal tissue, according to a study published in the journal Radiotherapy and Oncology. The findings may lead to the development of protocols that use soy isoflavones combined with radiation therapy in humans, a process they believe will yield both therapeutic and economic benefits.

Researchers at Wayne State University had shown previously that soy isoflavones increase the ability of radiation to kill cancer cells in prostate tumors by blocking DNA repair mechanisms and molecular survival pathways, which are turned on by the cancer cells to survive the damage radiation causes. At the same time, isoflavones act to reduce damage caused by radiation to surrounding cells of normal, noncancerous tissue.

Soy isoflavones can make cancer cells more vulnerable to ionizing radiation by inhibiting survival pathways that are activated by radiation in cancer cells but not in normal cells. In normal tissues, soy isoflavones also can act as antioxidants, protecting those tissues from radiation-induced toxicity.

For this study, the researchers investigated whether those results could prove true for non-small cell lung tumors in mice. They found the results "substantial" and "very promising."

The researchers noted soy supplements alone are not a substitute for conventional cancer treatment, and doses of soy isoflavones must be medically administered in combination with conventional cancer treatments to have the desired effects.

Preliminary studies indicate that soy could cause radioprotection," they said It is important to show what is happening in the lung tissue."

The next phase of the research will be to evaluate the effects of soy isoflavones in mouse lung tumor models to determine the conditions that will maximize the tumor-killing and normal tissue-protecting effects during radiation therapy.

If we succeed in addressing preclinical issues in the mouse lung cancer model showing the benefits of this combined treatment, we could design clinical protocols for non-small cell lung cancer to improve the radiotherapy of lung cancer," they said.  We also could improve the secondary effects of radiation, for example, improving the level of breathing in the lungs."

"In contrast to drugs, soy is very, very safe," Hillman said. "It's also readily available, and it's cheap.

"The excitement here is that if we can protect the normal tissue from radiation effects and improve the quality of life for patients who receive radiation therapy, we will have achieved an important goal."