Proton Therapy Case Study: HPV-related Squamous Cell Carcinoma of the Tonsil

Presentation and Examination

In May 2020, a 50-year-old healthy, nonsmoking man presented with a painless mass in the left neck and odynophagia for the preceding month.

Diagnosis

A contrast-enhanced CT scan of the neck revealed 3.2 cm and 1 cm cervical level II lymph nodes, with no obvious primary tumor. Subsequent fine-needle aspiration biopsy was performed on the left level II lymph node, which revealed a p16 (HPV) positive squamous cell carcinoma (SCC).

PET/CT scan confirmed an FDG-avid tumor was present in the left tonsil and lateral tongue base. Multiple FDG-avid lymph nodes in the left neck, levels II and III, were revealed, up to 3 cm. All were consistent with primary oropharyngeal SCC metastatic to left neck lymph nodes. There was no evidence of distant metastasis.

Treatment Options

The patient was offered surgical resection followed by radiotherapy with or without chemotherapy, or definitive chemoradiotherapy. Both were considered to be oncologically equivalent. The patient elected to pursue chemoradiotherapy. Proton radiotherapy was recommended for its ability to reduce excess dose to the oral cavity and oral tongue (affecting taste, mucositis, dry mouth), pharyngeal constrictors, larynx and esophagus (affecting swallowing and speech).

tonsils case study images

Compared with photon therapy, proton therapy has the potential to confer improved tumor control and reduce short- and long-term complications related to head and neck cancer therapy.

Key Takeaways

  • Proton radiotherapy spares significant excess dose to a number of critical structures, reducing the risk of the long-term detrimental side effects of radiotherapy.
  • The reduction of excess dose detailed here is of particular importance in a young, healthy patient with an excellent chance of recovery, because it potentially minimizes decades of long-term side effects.

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  • Side effects of radiation for head and neck cancers can impact taste, saliva, nutritional status, swallowing function and overall quality of life. In severe cases, patients may require nutritional support through feeding tubes or hospitalization for severe treatment associated toxicity. Proton therapy delivers less radiation to healthy tissue and thus reduces the incidence of these serious side effects.

Notes:

  1. Patel SH, Wang Z, Wong WW, et al. Charged particle therapy versus photon therapy for paranasal sinus and nasal cavity malignant diseases: a systematic review and meta-analysis. Lancet Oncol. 2014; 15(9): 1027-38.
  2. McDonald MW, Liu Y, Moore MG, et al. Acute toxicity in comprehensive head and neck radiation for nasopharynx and paranasal sinus cancers: cohort comparison of 3D conformal proton therapy and intensity modulated radiation therapy. Radiat Oncol. 2016; 11:32.
  3. Blanchard P, Garden AS, Gunn GB, et al. Intensity-modulated proton beam therapy (IMPT) versus intensity-modulated photon therapy (IMRT) for patients with oropharynx cancer—a case-matched analysis. Radiother Oncol. 2016; 120(1): 48-55.
  4. Romesser PB, Cahlon O, Scher E, et al. Proton beam radiation therapy results in significantly reduced toxicity compared with intensity-modulated radiation therapy for head and neck tumors that require ipsilateral radiation. Radiother Oncol. 2016; 118(2): 286-92.
  5. Blanchard P, Gunn GB, Lin A, et al. Proton Therapy for Head and Neck Cancers. Semin Radiat Oncol. 2018; 28(1): 53-63.
  6. Holliday EB, Esmaeli B, Pinckard J, et al. A Multidisciplinary Orbit-sparing Treatment Approach That Includes Proton Therapy for Epithelial Tumors of the Orbit and Ocular Adnexa. Int J Radiat Oncol Biol Phys. 2016; 95(1): 344-352.