Adjuvant Proton Radiation Following Transoral Robotic Surgery for HPV-Positive Oropharyngeal Squamous Cell Carcinoma

Introduction: Transoral robotic surgery (TORS) is a minimally invasive surgical technique used to resect oropharyngeal cancers, while proton beam therapy (PBT) may better spare normal nearby organs compared to traditional photon radiation, due to lack of exit dose. Research on the toxicity profile associated with PBT following TORS is limited.

Methods: Following IRB approval, we performed a retrospective review of all TORS cases performed in our department between January 2017 and December 2023. Patients with human papilloma virus (HPV) associated oropharyngeal squamous cell carcinoma (OPSCC), who received adjuvant PBT following TORS, were included. Patient demographics, disease characteristics, radiation parameters, acute and chronic radiation toxicities, and oncologic outcomes were extracted from the medical record.

Results: In total, 47 patients with HPV associated OPSCC underwent TORS and ipsilateral neck dissection, followed by PBT. Of them, 41 (87.2%) were male, with mean age 61.3 years (range 40.9-80.9). The majority of patients demonstrated T1-2 N1 disease. Most acute toxicities were reported as grade 1-2, with 1 (2.1%) patient experiencing grade 3 toxicities. Another 1 (2.1%) patient required placement of a nasogastric tube during the last week of adjuvant proton radiation, and 2 (4.3%) additional patients required gastrostomy tube placement. Duration of postoperative nasogastric tube requirement was longer in patients subsequently requiring feeding tube placement during treatment (p = 0.02), with a mean difference of 13 days (95% confidence interval 3-32). Median follow up was 17 months (range 2-51) from radiation. After the initial 6 months, chronic toxicities decreased in frequency. A (2.1%) patient developed regional recurrence, and 1 (2.1%) distant metastases.

Conclusions: Patients with HPV associated OPSCC treated with TORS followed by PBT demonstrate a favorable toxicity profile, with comparable oncologic outcomes. Patients experienced predominantly grade 1-2 acute toxicities with low rates of feeding tube placement. Chronic toxicities may decrease in frequency with time from PBT.