Rethinking Radiation Therapy for Perineural Invasion in Oral Cancer: Does More Coverage Improve Outcomes?

Area of Science:

• Oncology
• Radiotherapy
• Oral Cancer Research

Background:

• Perineural invasion (PNI) in oral squamous cell carcinoma (OSCC) correlates with aggressive disease and reduced survival.
• Adjuvant radiotherapy (RT) is standard for PNI-positive OSCC, but optimal target volume definition is unclear.

Purpose of the Study:

• To evaluate the impact of RT target volume on recurrence and survival in PNI-positive OSCC.
• To identify prognostic factors influencing outcomes in PNI-positive OSCC patients.

Main Methods:

• Retrospective analysis of 103 PNI-positive OSCC patients treated with surgery and adjuvant RT (with or without chemotherapy).
• Recurrence patterns (in-field, marginal, out-of-field) and survival outcomes (OS, DFS) were assessed.
• Prognostic factors were analyzed using univariate and multivariate models.

Main Results:

• The 2-year overall survival (OS) and disease-free survival (DFS) were 63% and 57%, respectively.
• In-field recurrences were common (70% of local failures), with no skull base recurrences despite conservative RT volumes.
• Extensive PNI, large nerve involvement, advanced tumor stage (T3/T4), extranodal extension (ENE), and depth of invasion >10mm were associated with poorer outcomes.

Conclusions:

• Expanding RT volumes to encompass entire cranial nerve pathways may not enhance outcomes and could increase toxicity.
• Personalized RT planning, considering PNI extent, nerve involvement, and other risk factors, is crucial for optimizing treatment in PNI-positive OSCC.