Bones rendered more vulnerable following radiation therapy

Researchers have found that mice who were given one therapeutic dose of radiation equal to that received by human cancer patients, lost as much as 39 percent of the spongy portion of their inner bone.

The loss according to the researchers meant their inner bone's weight-bearing connections was reduced by up to 64 percent.

Lead researcher Ted A. Bateman, a bioengineer at Clemson University who studies bone biomechanics,says they were really surprised at the extent of bone loss as it occurred after much lower doses of radiation than expected.

Bateman says that while the results of the mouse study cannot be directly applied to humans, it does raise concerns about radiation exposure.

He says the discovery could have implications for cancer patients receiving radiation therapy and the radiation exposure astronauts are exposed to on long space flights.

Clinical studies of people who undergo radiation to treat cancer are limited because of the complicating factors of the illness itself and the chemotherapy which often accompanies says Bateman.

Astronauts apparently lose 2% of bone mass for each month they are exposed to the effects of microgravity.

As yet no astronauts have been exposed to the increased radiation of outer space, but they will when they undertake a proposed 30-month trip to Mars says Bateman.

In the past NASA has focused it's attention on radiation's cancer-causing properties and whether it compromises the central nervous and immune systems and the effect on bone health has not been considered.

In the study the mice were given a single 2 Gray (Gy) dose, which is comparable to the single 1-2 Gy dose received by cancer patients, but they receive a series of doses over the course of their treatment, for a total of between 10 to 70 Gy.

The mice suffered a loss of trabecular bone, the spongy area of bone inside the dense outer cortical bone and this resulted in a less efficient bone support structure and leaves the bone more vulnerable to fractures.

The results support other research which has found that of 6,000 post-menopausal women who received pelvic radiation for cervical and colorectal cancer their bone fracture risk increased by 60% and radiation following anal cancer increased the risk of fracture by 200%.

The findings are published online in the Journal of Applied Physiology.