Four months into treating patients with head and neck cancers using pencil beam scanning with protons, Alexander Lin, MD, is optimistic about the results he is seeing so far. Many cancers are in remission and patients aren’t experiencing the life-changing side effects so common among those treated with conventional radiation.
When it comes to sheer cancer-killing power, “protons and photons are equally efficient,” said Dr. Lin, clinical operations director at Penn Medicine’s Roberts Proton Therapy Center in Philadelphia, Pennsylvania. Penn Medicine is the branded name for the University of Pennsylvania Health System. There, head and neck cancer tumors typically are removed by surgery before follow-up treatment with radiation.
“Cancer cells treated with proton or non-proton radiation can’t tell the difference at all,” he added.
But the after-effects of these radiation therapies is another story. Conventional radiation treatment can be far more pernicious to everyday living — during treatment and years after, said Dr. Lin, because the area of radiation tends to be wider, harming more healthy tissue.
Dr. Lin recalled the radiation dose images he viewed of his first head and neck patient who was treated with protons. “We saw an immediate lessening of the radiation dose to the oral cavity in our computer scans,” he said. “This is at the front part of the tongue, where all the taste buds are.”
Seeing less radiation affecting the taste buds, Dr. Lin was optimistic that his patient wouldn’t experience the taste problems that are common to patients treated with Intensity Modulated Radiation Therapy. “Every week we’d ask about taste,” Dr. Lin said. “He had no taste abnormalities.”
Able to taste food normally, Dr. Lin’s patient could hold his weight better during treatment and ensure optimal proton precision. “If people lose a large amount of weight during radiation treatments, the radiation precision can be compromised,” he added. “And protons are very sensitive to changes in the patient’s anatomy.
If the body changes slightly, it could be the difference between protons going where you want them or going where you don’t want them.”
Head and neck cancer patients treated with conventional radiation also may develop mouth sores, dry mouth and an inability to generate saliva, Dr. Lin said. Such treatment side effects are no mere inconveniences; they often have significant impacts on a patient’s quality of life, during and long after completion of therapy.
“If there is no saliva to help break down food, you can imagine the weight one would lose,” Dr. Lin said. “Dry mouth can affect quality of life, too.” And with an increasing percentage of conventional radiation patients, dry mouth is long lasting, affecting their ability to speak, he added. “Ameliorating these acute side effects tends to improve long-term outcomes,” he said.Optimally, direct comparisons of patient outcomes from those treated with protons as opposed to photons are needed to definitively conclude that protons are superior to photons for treating head and neck cancers, Dr. Lin noted; however he believes that in a few years, he and his collaborators at the University of Pennsylvania will be able to report such outcomes to confirm the clinical benefits of protons.
When treating certain head and neck cancers, unintended radiation exposure to the teeth, jaw and tongue, and its potential side effects may be reduced using protons (top), as compared to intensity modulated radiation therapy (bottom).
- (Images courtesy of Dr. Alexander Lin, Roberts Proton Therapy Center.)