Radiation therapy is mostly used for cancer treatment, but two studies presented at the annual American Association of Physicists in Medicine meeting have shown that it can also be useful for the treatment of high blood pressure and atrial fibrillation.

A combination of nerve signals and hormonal interactions between the brain, heart, blood vessels, and kidneys control blood pressure, and if those nerves are surgically removed or damaged, blood pressure could potentially be controlled. Currently, invasive surgical procedures are used to do that, but researchers at the Stanford University School of Medicine and Cancer Institute have started to explore the use of radiotherapy.

"We have the tools to accurately target these nerves that are responsible for communication between the brain and the kidneys," Peter Maxim, lead author of the study and assistant professor of radiation oncology at the university, said in a teleconference.

For the study, the researchers treated six pigs with high blood pressure with 40 Gy of radiation in a single treatment to the nerves around the arteries that lead to the kidneys. After a follow-up, they found that all of the pigs survived and had no adverse events.

After a pathology exam, they found that there was moderate damage to the nerves and only minimal damage to the nearby critical organs. Since the nerves were damaged, a nearly 30 percent drop in blood pressure was recorded at the three-month follow-up.

"Every animal survived and tolerated the treatment well, which demonstrated the safety of our study," said Maxim.

However, the researchers noted that although the drop in blood pressure is beneficial, it's not enough to bring it within a normal range. They didn't continue to track the pigs' blood pressure after three months, but they are planning on conducting a two-year follow-up study in order to find out the dynamic changes in blood pressure.

They have also sent a proposal to the institution review board at the university to conduct the first human study using the approach. It is still under review but they expect to start the first trial in either fall or winter of this year.

The other study presented at the meeting used a cardiac MR on four patients to determine if it could accurately image the heart as it's beating, in order to guide radiation therapy to treat atrial fibrillation.

It's most commonly treated with medication or ablation but ablation is invasive, time-consuming and expensive. Targeted radiation therapy can be used instead to treat the condition noninvasively in less than an hour.

However, it's tricky to image the heart accurately while it's beating. The goal is to reach the target with radiation therapy without damaging either the heart or the surrounding tissue.

"The challenge is that the heart is beating and also the heart is moving with respiration," said Paul Keall, lead author of the study and professor of medicine at the University of Sydney, during a teleconference. "We need very precise imaging and marrying that to adaptive radiotherapy enables this treatment to happen."

Right now, the researchers are working on developing the cardiac MR further and then they will test it on patients.

"It will enable us to treat cardiac disease with radiation and address a major medical problem and hopefully be able to treat patients more cost effectively with less morbidity," said Keall.

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