A study published Wednesday in Science Translational Medicine, presents a new mathematical equation that more accurately calculates large radiation doses for cancer treatment.

Research has shown that the quadratic equation normally used to calculate radiation dose falls short when it comes to measuring large doses, according to the Ohio State University scientists. While the conventional formula is effective for small, long-term doses, explained senior author Nina Mayr, it doesn't work well for large doses. And often, patients prefer the large doses because they don't have to return for as many treatments.

"The old equation, perhaps, overestimates cell killing in the high-dose range," she told DOTmed News. "It estimates properly if it's closer to conventional doses, but way out on a limb into the high-dose area, it may be overestimating."
A high dose is more than 5 or 6 Grays of radiation, while the conventional doses are 1.8 to 2 Grays.

High doses of radiation are primarily used for brain, prostate and lung tumors, said Mayr.

According to the report, scientists think that radiation causes two types of human cell DNA lesions: lethal and sub-lethal. Lethal lesions cause immediate cell death, while sub-lethal can cause reparable injury or injury that can become lethal if hit with more radiation. Overestimating the radiation dose could lead to inadequate treatment, the report stated.

In order to test the new equation, the researchers measured the effects of different doses of radiation on cell grown in the lab and in animals.

"We found an equation to make [the data set] fit with the low and high doses," explained Mayr. "That means...how to respond to low doses can now be translated through this equation if you want to give it as a higher dose."

The equation is still in the experimental stages, next being tested against human patients.

"When we first applied large dose treatments...we were literally guessing, 'What dose do I give? What dose would be safe? How high can we go? High enough to kill a tumor but not too high for normal tissue to [get] damaged,'" said Mayr. "People had to do a lot of estimations that were difficult...because you had nothing to go by. Now, with the new equation, we have a scientific model we can go by."

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