Objectives: Patients treated with definitive chemoradiation for oropharyngeal squamous cell carcinoma (OPC) experience excellent outcomes but treatment toxicities remain significant. The adoption of intensity modulated radiation therapy (IMRT) reduced morbidity by allowing targeting of at risk areas while sparing uninvolved regions. We explored whether level V lymphatics (LVN) can be omitted from elective volumes in OPC.
Materials and methods: This analysis included 408 patients treated for stage III/IV OPC with IMRT at our institution. For 295 (72.3%) patients, bilateral LVN were covered, while LVN were omitted in 113 (27.7%). Nodal staging was N2a or greater in 324 patients (79.4%). All but one received concurrent chemotherapy. Actuarial regional recurrence was calculated using the KM method with the event of interest defined as any regional recurrence; all others were censored. Univariate and multivariate analyses were performed on variables significantly associated with both the inclusion of elective LVN and regional recurrence.
Results: After a median follow-up of 63.6months (range, 1.3-125months), there were no level V failures in either group. The 2-year cumulative rate of regional failure (RF) was 4.5% (95% CI=2.9-6.6) in the overall cohort, 2.2% (95% CI=0.1-5.9) in the LVN untreated group, and 5.4% (95% CI=3.4-8.1) in the LVN treated group. After adjusting for Stage and tobacco status, there was no significant difference between the two groups in RF (HR=1.75 95% CI=(0.61-5.07), p=0.30).
Conclusion: LVN can be safely omitted from the clinical target volume in locally advanced OPC without gross LVN involvement.
Keywords: Clinical target volume; HPV; IMRT; Level V; Oropharyngeal cancer; Radiation therapy; Volume de-escalation.
Copyright © 2016. Published by Elsevier Ltd.