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Protons for Head & Neck Cancers

Protons for Head & Neck Cancers

April is Head & Neck Cancers Awareness Month, an excellent time to highlight proton therapy as a treatment option.

What are head and neck cancers? According to the National Cancer Institute, "Cancers that are known collectively as head and neck cancers usually begin in the squamous cells that line the moist, mucosal surfaces inside the head and neck (for example, inside the mouth, the nose, and the throat)." Head and neck cancers usually fall into several categories based on where they originate, including oral cavity, pharynx, larynx, sinuses and nasal cavity, salivary glands, thyroid gland, and skin of the face, neck, and scalp. Because the head and neck region has a variety of critical structures tightly packed together - the optic structures, organs of hearing, brain, brain stem, spinal cord, salivary glands, muscles of swallowing, taste buds to name a few - it can be difficult to target nearby cancers, while minimizing damage to the critical structures using conventional radiation, which is why protons can be beneficial. 

"In general, protons reduce exposure of normal structures to unnecessary radiation," says Dr. Upendra Parvathaneni, our head and neck cancers expert at the Center. "In particular, normal (healthy) structures that are away from the targets are spared from low to intermediate doses of radiation. Minimizing unnecessary radiation to these structures is intuitively desirable." Dr. Parvathaneni and his colleagues just published a study recently on proton therapy for oropharyngeal cancer

Protons can be manipulated to release their energy at a precise point. The amount of proton energy is calculated to release the proton radiation precisely at the tumor site. Immediately after that point, the radiation dose falls to zero. Because of this, the use of proton therapy reduces the likelihood of side effects such as blindness, hearing deterioration, and dry mouth. Secondary malignancies are also less likely with proton therapy.

Conversely, X-rays are electromagnetic waves that penetrate tissue, gradually losing energy as they move along. The highest radiation dose occurs shortly after entering the body. That means much of the radiation is deposited in the healthy tissue in front of the tumor. After treating the tumor, the X-rays continue to deposit radiation dose and affect healthy tissue as it leaves the body (exit dose). That can cause a variety of short- and long-term side effects, some of which can seriously affect quality of life and health.

The above image illustrates the difference in amount of radiation exposure in conventional radiation (left) and proton beam radiation (right). 

Depending on the anatomy of each cancer, some patients could benefit immensely from proton radiation and experience much fewer side effects, whereas other patients will see a smaller difference between the two types of radiation.

Dr. Parvathaneni explains: "The closer the targets are to the critical structures like brain or optic structures, the greater the anticipated benefit of using proton therapy. We would typically use proton therapy for the following tumors: nasopharynx, sino-nasal (para-nasal sinuses), orbital, skull base (aggressive skin cancers with peri-neural spread along cranial nerves), paragangliomas and schwannomas near the skull base, and re-irradiation. We use proton therapy for more than 90% of these types of tumors." 

Skull-base tumors like chordomas also have an established indication for proton therapy, and are also seen by the Central Nervous System team at the Center.

Head and neck cancers are often linked to tobacco (including smokeless tobacco) and alcohol use. These are the most important risk factors; however, over the past decade, an increasing number of young, non- smokers have developed mouth and throat cancer associated with the human papillomavirus, or HPV. This most often presents as a painless lump in the neck that does not resolve with a course of antibiotics. There are often no throat symptoms. You should ask for a referral to a specialist if you have a lump in the neck. You should also speak to your health care professional about how often to have check-ups, especially if you smoke or drink. As with most cancers, early detection means the cancer is easier to treat and cure and is less likely to have spread to other parts of the body.

Please see our Head and Neck Cancers webpage for more information.