Writing in Radiotherapy and Oncology, researchers report that soy isoflavones enhanced the destruction of lung tumours by radiation, whilst also reducing vascular damage, inflammation and fibrosis caused by radiation injury to normal lung tissue.
The team, led by Dr Gilda Hillman, ofWayne State University, USA, said their findings suggest a complimentary approach could be applied to the treatment of patients with advanced lung cancer (non-small-cell lung carcinoma). They argued that radiation toxicity could be lessened by the protective effects of soy isoflavones on normal lung tissue.
“Soy could be used as a non-toxic complementary approach to improve radiotherapy,” said the research team, adding that in particular, patients with already compromised lung functions, such as in smokers, “could particularly benefit from this complementary approach.”
However, Hillman emphasised the soy supplement was not a substitute for conventional cancer treatment, and that doses of soy isoflavones must be taken in combination with conventional cancer treatments to have the desired effects.
“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,” said Hillman.
“In contrast to drugs, soy is very, very safe,” she added, “It’s also readily available, and it’s cheap.”
Hillman explained that previous research has shown soy isoflavones – a natural, nontoxic component of soybeans – to increase the ability of radiation to kill cancer cells in prostate tumours by blocking DNA repair mechanisms turned on by the cancer cells to survive the damage radiation causes.
In the new study the team used a mouse model of lung cancer to investigate the potential use of oral doses of soy isoflavones as a strategy to improve radiotherapy outcomes.
The team found that compared to lung tumours treated with soy isoflavones or radiation, those given both showed improved radiation-induced destruction of lung tumour nodules. They added that the soy isoflavones also decreased haemorrhages, inflammation and fibrosis caused by radiation in lung tissue – “suggesting protection of normal lung tissue.”
Hillman said her findings were “substantial” and “very promising,” but that further research is still needed. The next step, she said, will be to evaluate the effects of soy isoflavones in mouse lung tumour models to determine the conditions that will maximize the tumour-killing and normal tissue-protecting effects during radiation therapy.
After that, she said that with the correct protocols in place, clinicians could begin to use soy isoflavones combined with radiation therapy in humans – a process she believes will yield both therapeutic and economic benefits.
Source: Radiotherapy and Oncology
Volume 101, Issue 2, Pages 329-336, doi: 10.1016/j.radonc.2011.10.020
“Soy isoflavones radiosensitize lung cancer while mitigating normal tissue injury”
Authors: G.G. Hillman, V. Singh-Gupta, L. Runyan, C.K. Yunker, J.T. Rakowski, F.H. Sarkar, et al