KEY POINTS
- The EXTENT study retrospectively analyzed 410 postoperative oral cavity squamous-cell carcinoma patients treated with adjuvant radiotherapy or chemoradiotherapy from 2019–2024. PNI was present in 296 patients, ENE in 185, and both in 71; median follow-up was 33 months.
- All patients received VMAT with simultaneous integrated boost. Standard postoperative treatment prescribed 60 Gy and 54 Gy in 30 fractions to high- and low-risk volumes; close-margin cases received 64 Gy and 57.6 Gy in 32 fractions. Weekly cisplatin 40 mg/m² was used when concurrent chemotherapy was indicated.
- Across the entire cohort, estimated 3-year disease-free survival was 45.6% and 3-year overall survival 53.2%. Disease progression occurred in 182/410 patients (44.3%), including 101 locoregional and 81 distant failures.
- Among patients with PNI, intratumoral PNI was present in 246 and extratumoral PNI in 50. Median disease-free survival was 36 versus 17 months, and 3-year disease-free survival was 49.5% versus 43.3% (p=0.019) for intratumoral versus extratumoral disease.
- Overall survival also separated by PNI extent: 3-year OS was 57.9% with intratumoral versus 50.2% with extratumoral PNI (p=0.02). One-year locoregional recurrence-free survival was 56.1% versus 20.0% (p=0.047), whereas distant-metastasis-free survival did not significantly differ (p=0.67).
- ENE extent was much less informative. Among 112 microscopic and 73 macroscopic ENE cases, there was no significant difference in disease-free survival (p=0.30), overall survival (p=0.45), locoregional recurrence-free survival or distant-metastasis-free survival.
- Multivariable subgroup analyses identified the combination of extratumoral PNI, macroscopic ENE and lymph-node ratio >0.05 as a particularly adverse phenotype. The authors explicitly frame treatment intensification for this subgroup as hypothesis-generating rather than established practice.
CLINICAL TAKEAWAY
For postoperative oral cavity cancer, where the tumor grows along the nerve may matter more prognostically than whether ENE extends just below or above the 2-mm threshold. Extratumoral PNI deserves careful pathology reporting and may be useful for risk stratification, but this retrospective study does not establish a new indication for systemic or radiotherapy intensification.