New Accelerator Tech Will Help To Kill Off Tumors With Quick Radiation Pulses

Generally, brachytherapy (BT) and external beam radiation therapy (EBRT) are the two types of radiation techniques that are used clinically. In BT, the radiation device is placed within or close to the target volume. EBRT uses a device located at a distance from the patient, as in the case in most orthovoltage or supervoltage machines. The arrival of high-voltage EBRT for deeper tumors and problems associated with radiation exposure to high-energy radionuclides, led to a decrease in using BT as a treatment option till the middle of last century. However, over the past three decades, there has been renewed interest in the use of BT. The discovery of man-made radioisotopes and remote afterloading techniques has reduced radiation exposure hazards. Innovative imaging modalities (computed tomography, magnetic resonance imaging, transrectal ultrasound) and sophisticated computerized treatment planning systems has helped to achieve an increased positional accuracy and superior, optimized dose distribution. Finally, while BT was initially used only for cancer treatment, some years ago it has been discovered to be helpful in non-malignant diseases (for example, in prevention of vascular restenosis, in keloids treatment). It is clear that BT is the optimal way to deliver conformal radiotherapy that is tailored to the shape of the tumor, while sparing surrounding normal tissues.

There are two main types of radiation therapy: photon-based and ion-based. Photon-based therapies use focused beams of electromagnetic radiation in the X-ray or gamma-ray frequency ranges to kill cancer cells within tumors. The downside is that photon-based therapy also damages the healthy tissue in front of and behind the tumor in the path of the beam. Accelerated ions like protons behave differently. They deposit a low amount of energy in matter they encounter at the beginning of their path and a very high burst at the end, right before stopping completely. This phenomenon allows scientists to plot precise beam paths that deliver large radiation doses to tumors with minimal damage to tissue in front and no damage to tissue behind.

New Accelerator Tech Will Help To Kill Off Tumors With Quick Radiation Pulses

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As there are a variety of particles that can deliver radiation to tumors, there are also many different ways to parse out the energy. The hit-it-fast-and-hard paradigm of FLASH radiotherapy has tantalized radiobiologists since the 1960s, when lab-based experiments suggested that FLASH dose rates can kill cancer cells while sparing a larger proportion of healthy tissue than treatments with longer, lower energy doses. However, the approach is not yet widely approved.

Cengel and his colleagues plan to continue optimizing their tools and techniques while working to determine what dose rate delivers the most therapeutic benefit. In this way, the team would run a clinical trial of sorts but with animals as the initial subjects. Meanwhile, Vozenin and her colleagues will soon launch the first clinical trials in human patients in order to test their own flash techniques. Using low-energy electrons, they aim to treat superficial tumors, such as those seen in skin cancers.

"If we can validate the flash concept in large volume and in clinical applications, then it will probably change all radiation therapy," Vozenin said. She said she expects that some version of flash radiation might be widely available to cancer patients within the next 10 years. Favaudon said that treatments targeting surface tumors, as well as those exposed through surgery, could be ready within two years. Techniques using high-energy electrons and proton beams could be ready within five to 10 years, he said.

Using beams of accelerated protons or heavier ions such as carbon, oncologists can deliver cell-killing energy to precisely targeted tumors -- and do so without causing extensive damage to surrounding healthy tissue, eliminating the major drawback of conventional radiation therapy using x-rays. 2ff7e9595c