Adaptive radiotherapy is a form of radiation therapy that takes the pinpoint targeting of radiation to a new level of personalization for patients. Like regular radiation therapy, adaptive radiotherapy utilizes a focused plan and delivery of radiation to treat a tumor in a patient, while trying to limit the amount of surrounding healthy tissue affected by radiation.
However, adaptive radiotherapy takes this further by reassessing the status of the targeted tumor on a daily basis and adjusting the delivery of treatment to maximize effectiveness.
According to Yves Archambault, Strategic Initiative Director at Varian, the idea driving adaptive radiotherapy is that the surrounding healthy tissue acts as a limiting factor for how aggressive radiation therapy can be without damaging the rest of the body. By regularly reassessing and adjusting, it’s possible to reduce this limitation of cancer treatment. The hope is that patient outcomes will improve for more difficult cancers including pancreatic cancer, which currently has some of the lowest survival rates.
Treatment is similar to regular radiation therapy with patients coming into the clinic two to three times a week for radiation doses for several weeks. Adaptive radiotherapy utilizes extensive imaging to visualize every aspect of the tumor and surrounding tissue, requiring patients to lay down in a confined space for long periods of time while the equipment does its job. Patients who have trouble staying in claustrophobic spaces for long periods of time will find treatment days difficult.
Major challenges remain for more widespread implementation of adaptive radiotherapy. The imaging technology used to visualize the tumors, magnetic resonance imaging (MRI), is costly, complex, and requires extensive facilities to house the machinery. Due to the nature of magnetics, patients cannot have any metal on their person. Even those with metal alloy implants may be prohibited from undergoing this type of therapy as only specific kinds of metal alloy implants are acceptable in the MRI room. The MRI machine is also responsible for the claustrophobic space patients have to lie in while they are imaged.
For now, adaptive radiotherapy is limited to a few locations around the United States, and with high costs and long treatment days, many patients don’t have access to this treatment or might be deterred by the process.
New Imaging Methods
In the future, clinicians using adaptive radiotherapy want to move away from relying on MRI to provide imaging for treatment. With improvements on imaging technologies and interpretation and the treatment devices themselves, companies like Varian hope to switch to cone beam computed tomography (CBCT) for adaptive therapy imaging. Based on traditional CT scan technology, CBCT uses a cone-shaped beam of x-ray to construct a 3D image in one motion rather than a series of slices of x-ray like traditional CT scans. A transition to CBCT for adaptive therapy imaging would offer a variety of benefits for both patients and providers.
CBCT equipped radiotherapy devices are cheaper to operate than MRI equipped radiotherapy devices. Facility requirements and disallowance of metal implants aren’t as strict for CT-type scans as they are for MRIs because CT-type scans use x-rays instead of magnetic fields to develop detailed images of the body.
While CBCT-based adaptive therapy also requires a patient to lie still as the machine scans and treats them, the time spent is much shorter than with MRI-based adaptive therapy, lasting anywhere from seconds to a few minutes. In contrast, MRIs sometimes take longer than an hour to complete a scan. Reduced imaging times would lessen the burden on patients and increase the number of patients that could be treated in a day.
While adaptive radiotherapy based on CBCT is not quite there yet, it’s a promising direction. More cancer treatment centers would be able to utilize adaptive radiotherapy, increasing availability to patient populations, improving the daily strain of cancer treatments and reducing costs for patients already burdened with high medical expenses.
For patients facing the daunting gauntlet of cancer treatment, adaptive radiotherapy gives increased hope for tumor control and longer life expectancy for many kinds of cancers. Adaptive radiotherapy adds more personalization to treatment plans and shows promise for difficult cancers or advanced stage cancers that cannot normally be operated on.
With further improvements and expansion of access, adaptive radiotherapy will be a tremendous development for radiation therapy for many cancer patients across the United States.
Featured photo used as a reference only, not an accurate depiction of an adaptive radiotherapy machine.