Soy may help protect lungs from radiation damage in NSCLC

Hillman GG. J Thorac Oncol. 2013;doi:10.1097/JTO. 0b013e3182a4713e.

  • December 23, 2013

Soy isoflavones administered before and after radiation protected lungs against adverse effects, including skin injury, hair loss, increased breathing rates, inflammation, pneumonitis and fibrosis, according to study results published in the Journal of Thoracic Oncology.

In a preclinical lung tumor model, soy isoflavones exhibited the potential to enhance radiation damage in tumor nodules while simultaneously protecting noncancerous lung tissue from radiation injury.

To determine whether supplementation with soy isoflavones could improve high-dose radiotherapy for inoperable non–small cell lung cancer by alleviating radiation injury to lung tissue, researchers treated naive Balb/c mice with oral soy isoflavones for 3 days before and up to 4 months after radiation.

Radiation was administered to the left lung at 12 Gy. Mice were examined for toxicity and breathing rates at 2, 3 and 4 months after radiation. Lung tissues also were processed for histology for in situ evaluation of response.

According to study results, supplementation with soy isoflavones protected mice against radiation-induced skin injury and hair loss. Lung irradiation was found to cause an increase in breathing rate that was more pronounced by 4 months after radiation, due to the late effects of radiation-induced injury to normal lung tissue. However, this effect was mitigated by soy isoflavones.

Upon histological examination, irradiated lungs exhibited a chronic inflammatory infiltration involving alveoli and bronchioles and a progressive increase in fibrosis, which were alleviated by soy isoflavones.

“Our experimental studies in animal models suggest that the addition of soy to radiotherapy might improve the effect of radiotherapy on the tumor target and reduce the dose-limiting toxicity of radiotherapy to the normal lung,” the researchers wrote. “If this proves to be the case, this simple, nontoxic, natural compound would radically improve the effectiveness of this new radiation treatment for inoperable NSCLC.”

Disclosure: The researchers report no relevant financial disclosures.

Perspective

Mohamed Abazeed

  • The prevention and mitigation of radiation-induced injuries impacts several aspects of public health and medicine. The explosion of a low-grade radiological weapon by terrorists, the outbreak of nuclear conflict, and nuclear power plants accidents (a la Chernobyl and Fukushima) can cause initial deaths and contaminate land, water, air, and food sources leading to increased risk of radiation-induced damage for decades. The growing use of X-ray-based diagnostics and procedures raises concerns about long-term health risks. Radiation is also used an important and common therapeutic option for a number of cancers, but its use is frequently limited due to adverse effects on normal tissues. Minimizing harmful side effects of radiation has significant implications for the public and patients.

    This study demonstrates that soy isoflavones, which are dietary plant estrogens extracted from soy beans, protect mice from radiation-induced adverse effects including skin injury, hair loss, increased breathing rates, inflammation, pneumonitis and fibrosis, providing evidence for a radioprotective effect of soy. There are several encouraging preclinical studies demonstrating radioprotection of a variety of cells and tissues by several chemicals. However, radioprotectors would not be expected to increase the cancer therapeutic ratio unless they could be introduced into or selectively function in normal tissues but not tumors. Interestingly, soy isoflavones appear to exhibit anti-tumor effects while protecting normal tissues (Radiother Oncol. 2013 Sep 7. doi: 10.1016/j.radonc.2013.08.015.), appearing to satisfy the important principal of differential activity in tumor and normal tissue.

    Further testing of soy isoflavones in more physiological animal tumor models will be necessary before clinical implementation in lung cancer treatment since previous data suggest optimal modeling of the response of tumors to radiation requires an intact immune system. This will build on the preliminary data that soy isoflavones show promise as effective radiation protectors and mitigators in patients with lung cancer.

    • Mohamed Abazeed, MD, PhD
    • Associate staff physician
      Department of radiation oncology
      Cleveland Clinic Taussig Cancer Institute
  • Disclosures: Abazeed reports no relevant financial disclosures.