Proton Therapy Shows Promise in Head and Neck Paragangliomas

Patients with head and neck paragangliomas may be safely and effectively treated with proton therapy, with comparable results to those treated with conventional photon radiotherapy strategies, according to findings published in Head & Neck.

Head and neck paragangliomas are rare, usually benign, neuroendocrine tumors that form in a group of nerve cells in the nervous system that allow the nerve cells to form anywhere along the sympathetic and parasympathetic nervous systems. There are two types: chromaffin paragangliomas and nonchromaffin paragangliomas.

These tumors commonly arise in or along the temporal bone, jugular foramen, vagus nerve or carotid body.

Surgery and radiation therapy are the current standard of care, with radiation growing in popularity because of the morbidity associated with removing head and neck paraganglioma from the jugular foramen.

“The primary goal of therapy is to arrest tumor growth while minimizing morbidity,” the researchers wrote. “…Although the main objective of radiation therapy is to halt growth of the existing tumor, it can additionally provide volumetric shrinkage and improvement of (head and neck paraganglioma)-associated symptoms.”

While radiation use increases, the decision to use proton or photon radiotherapy also ensues. However, proton therapy has been found to reduce the collateral radiation dose to surrounding normal tissues, which in head and neck paraganglioma, can spare the oral cavity, brain, brainstem, cochlea, oropharynx and skin.

“Because of the near proximity of these functionally critical structures, there is compelling rationale to consider the utility of protons for radiation management of these tumors,” the researchers wrote.

In this retrospective review, they reported on their experience of using proton therapy in 37 patients (40 tumors overall) with head and neck paragangliomas treated at a single institution from 1997 to 2016 to determine the safety and efficacy of the regimen.

Proton therapy was delivered to a median of 50.4 Gy.

Consistent with the fact that these tumors occur as a result of family risk in 30%-40% of cases, the researchers found that having a genetic/family predisposition for the disease was associated with multifocal tumors, as well as younger diagnosis age. “…both factors in which the selective utility of proton therapy may significantly benefit patients,” the researchers explained.

Twenty-six patients (70%) had symptom improvement after treatment with proton therapy. The most commonly improved symptoms included dysarthria (67%), tinnitus (57%), aural pain/pressure (33%) and headache (33%). In addition, 65% of treated tumors showed 20% or more of volumetric shrinkage.

Moreover, the five-year recurrence-free and overall survival rates were both 97%.

Grade 2 to grade 3 side effects included subjective hearing impairment (19%), middle ear inflammation (14%) and dry mouth (8%).

“Patients with (head and neck paragangliomas) can be effectively and safely treated with proton therapy with achievement of excellent (recurrence-free survival), successful volumetric tumor reduction and symptomatic improvement in most cases,” the researchers concluded. “These results are comparable to those achieved with conventional photon radiotherapy strategies. Proton therapy may be especially compelling to consider for patients with susceptible genetic mutations and/or family history of (head and neck paragangliomas), multifocal disease or younger age at diagnosis.”