Complete Pathological Response of Human Papillomavirus (HPV)-Related Oropharyngeal Carcinoma After Primary Treatment With Stereotactic Radiotherapy: A Case Report.

Human papillomavirus (HPV)-related oropharyngeal squamous cell carcinomas (OPSCCs) with locally advanced progression are generally treated with curative intent concurrent chemoradiation. This case report of a 51-year-old female highlights the potential for locoregional control with complete pathologic response following primary stereotactic body radiotherapy (SBRT). Previous studies on SBRT for head and neck cancers report variable dose fractionation schemes and inconsistent volume contouring techniques, with most SBRT applications focused on recurrent or post-operative settings rather than definitive primary treatment. In this case, the patient initially presented with palpable left cervical lymphadenopathy. Diagnostic workup confirmed non-keratinizing invasive squamous cell carcinoma of the left base of the tongue, with strong p16 positivity. After declining standard curative intent treatment options, including chemoradiation, the patient later accepted a palliative SBRT regimen of 40 Gy in five fractions weekly, targeting the oropharynx and unilateral neck. The patient ultimately only received 32 Gy in four fractions. Follow-up imaging demonstrated significant tumor regression, but at five months, a palpable L neck mass remained. A subsequent selective neck dissection confirmed complete pathologic response with no residual carcinoma. The patient remained disease-free 68 months after treatment with minimal late toxicities. This case supports the feasibility of using SBRT as a definitive modality for HPV-related OPSCC, highlighting the potential for durable locoregional control with an acceptable toxicity profile. Given the growing interest in both treatment de-escalation for HPV-related OPSCC and the application of SBRT in head and neck cancers, this report suggests a promising, though preliminary, role of SBRT in selected patients.