'Zapping tumours may reduce side effects of cancer therapy'

Scientists in the US are developing a new technology that can reduce the side effects of cancer radiation therapy by shrinking its duration from minutes to under a second.

Built into future compact medical devices, the technology -- which is used for high-energy particle physics -- could also help make radiation therapy more accessible around the world.

The researchers from US Department of Energy's SLAC National Accelerator Laboratory and Stanford University are working on two projects to develop possible treatments for tumours -- one using X-rays, the other using protons.

The idea behind both is to blast cancer cells so quickly that organs and other tissues do not have time to move during the exposure -- much like taking a single freeze frame from a video.

This reduces the chance that radiation will hit and damage healthy tissue around tumours, making radiation therapy more precise.

"Delivering the radiation dose of an entire therapy session with a single flash lasting less than a second would be the ultimate way of managing the constant motion of organs and tissues, and a major advance compared with methods we're using today," said Billy Loo, an associate professor at Stanford.

"In order to deliver high-intensity radiation efficiently enough, we need accelerator structures that are hundreds of times more powerful than today's technology. The funding we received will help us build these structures," said Sami Tantawi, chief scientist for the RF Accelerator Research Division in SLAC's Technology Innovation Directorate.

In today's medical devices, electrons fly through a tube-like accelerator structure that's about a metre long, gaining energy from a radiofrequency field that travels through the tube at the same time and in the same direction.

The energy of the electrons then gets converted into X-rays. Over the past few years, the team has developed and tested accelerator prototypes with special shapes and new ways of feeding radiofrequency fields into the tube.

These components are already performing as predicted by simulations and pave the way for accelerator designs that support more power in a compact size.

"Next, we'll build the accelerator structure and test the risks of the technology, which, in three to five years, could lead to a first actual device that can eventually be used in clinical trials," Tantawi said.

In principle, protons are less harmful to healthy tissue than X-rays because they deposit their tumour-killing energy in a more confined volume inside the body.

However, proton therapy requires large facilities to accelerate protons and adjust their energy. It also uses magnets weighing hundreds of tonnes that slowly move around a patient's body to guide the beam into the target.

"We want to come up with innovative ways to manipulate the proton beam that will make future devices simpler, more compact and much faster," said Emilio Nanni, a staff scientist at SLAC, who leads the project with Tantawi and Loo.

In addition to making cancer therapy more precise, flash delivery of radiation also appears to have other benefits.

"We've seen in mice that healthy cells suffer less damage when we apply the radiation dose very quickly, and yet the tumour-killing effect is equal to or even a little bit better than that of a conventional longer exposure," Loo said.

"If the result holds for humans, it would be a whole new paradigm for the field of radiation therapy," he said.

Another key objective of the projects is to make radiation therapy more accessible for patients worldwide.

Today, millions of patients around the world receive only palliative care because they don't have access to cancer therapy, Loo said.

"We hope that our work will contribute to making the best possible treatment available to more patients in more places," he said.