Technical details and clinical outcomes after high-dose-rate intracavitary brachytherapy for squamous cell carcinoma of external auditory canal and external beam radiotherapy for nodal coverage: A case report

Introduction:
To report technical details and 15-month outcomes of a patient with node-positive external auditory canal (EAC) squamous cell carcinoma (SCC) treated with definitive intracavitary high-dose-rate (HDR) brachytherapy to primary tumor, and external beam radiotherapy (EBRT) to draining lymphatics.

Material and methods:
A 21-year-old male was diagnosed with SCC of the right EAC. The patient underwent definitive HDR intracavitary brachytherapy, 340 cGy/fraction for 14 twice-daily fractions, followed by EBRT using intensity-modulated radiation therapy (IMRT) to cover the grossly enlarged pre-auricular node, ipsilateral intra-parotid, and cervical lymph node levels II and III.

Results:
The approved brachytherapy plan had an average high-risk clinical tumor volume (CTV-HR) D₉₀ of 341 cGy with a total dose of 47.7 Gy (BED, 80.3 Gy, EQD₂, 66.6 Gy). For the approved IMRT plan, the prescription to the involved right pre-auricular node was 66 Gy in 33 fractions, and more than 95% of the target received at least 62.7 Gy. High-risk nodal regions were simultaneously prescribed: 59.4 Gy in 1.8 Gy fractions, and more than 95% received at least 56.4 Gy. Organs at risk (OARs) were kept below their dose constraints. The patient tolerated both the procedures with no grade ≥ 2 treatment-related adverse events. Grade 1 dermatitis in the right pre-auricular and cervical areas during the course of EBRT was experienced. Fifteen months post-RT, the patient has no evidence of disease, and was noted to have EAC stenosis, which translated to moderate conductive hearing loss of the right ear. Thyroid function was normal at 15 months after EBRT.

Conclusions:
This case report illustrates that the delivered definitive radiotherapy is technically feasible, effective, and well-tolerated in patients with SCC of EAC.