Locoregional Skull Base Recurrence Masked by Chronic Otomastoiditis in a Patient with HPV-Related Oropharyngeal Squamous Cell Carcinoma Treated with Primary Chemoradiation

Background: HPV-related oropharyngeal squamous cell carcinoma (OPSCC) presents at more advanced stages than HPV-negative OPSCC, but since it is more responsive to chemotherapy and radiation has better overall survival. Interestingly, outcomes differ between HPV-related OPSCC smokers as compared with non-smokers, with studies indicating locoregional and distant recurrence rates of 37 versus 21% at 24 months respectively. Additionally, the recurrence patterns of smokers with HPV-positive disease mirror those of HPV-negative patterns with primarily (70–79%) locoregional disease recurrence.[1]

Case: A 61-year-old male with 20 pack-year smoking and drinking history, and 20-year history of chronic right otomastoiditis, presented to a community otolaryngologist in 2017 with odynophagia. An indurated soft palate lesion was identified and biopsy revealed p16+ invasive moderately differentiated OPSCC. Initial staging PET-CT showed FDG-avid mass of SUV 8.6 involving right soft palate with extension beyond the nasopharynx, into the petrous apex, floor of middle cranial fossa, lateral margin of the sphenoid and anterolateral basiocciput, with high probability for perineural involvement at the level of the vidian canal and foramen rotundum. Staged as T3N1M0 after imaging, he was definitively treated with concurrent weekly Cisplatin and intensity-modulated radiation therapy. The oncologic physician at the time of diagnosis recommended further Otolaryngology evaluation to address the mastoiditis; however, no surgery or biopsy was done. Six-month surveillance imaging showed ongoing skull base lesion involving the petrous bone ([Fig. 1]), although notes mention this could be secondary to chronic otomastoiditis. In January, 2019 the patient developed diplopia with lateral gaze palsy and subsequent right facial nerve paralysis prompting repeat imaging. CT and MRI showed an expansile invasive mass at right petrous apex extending to midclivus and right mastoid bone ([Figs. 2] and [3]), with critical finding of encasement of the mastoid portion of the right ICA. The patient underwent BTO with right carotid embolization by interventional neurosurgery, followed by right transcanal biopsy with mastoidectomy and petrous apicectomy. Intraoperative biopsies showed p16+ OPSCC disease of the EAC, as well as in the deep mastoid segment. He was treated with 2 weeks of IV antibiotics with improved House–Brackmann score at follow-up, and returned to home onocologists for chemoradiation treatment.

Discussion: It is possible that in this case the patient had locoregional extent to the skull base initially, and with history of otomastoidits potentially masking malignancy, no tissue diagnosis of skull base was completed at the time. It is important to be vigilant about diagnosis and disease extent, especially in smokers with HPV+ disease, as this may have warranted more expanded radiation or chemotherapy regimen.

• References

• Liu C, Talmor G, Low GM, et al. How does smoking change the clinicopathological characteristics of human papillomavirus-postive oropharyngeal squamous cell carcinoma?? One medical center experience. Clin Med Insights Ear Nose Throat 2018; 11: 1179550618792248