Objectives: To determine the effect of postoperative radiation therapy for salivary gland carcinomas in the presence of microscopic perineural invasion. Design and setting: Retrospective review at an academic tertiary center. Participants: One hundred and forty patients with pathological evidence of perineural invasion at the time of initial surgery for salivary gland carcinomas were analysed. Sixteen patients (11%) had major (named) nerve involvement. Ninety-four patients (67%) received postoperative radiation therapy to the primary site, and the portal films of 65 of these patients were available for review. Main outcome measures: The incidence of skull base recurrences among patients treated by surgery with or without postoperative radiation therapy. Results: Ten patients experienced skull base recurrences. T4 disease and the omission of postoperative radiation therapy were identified as significant predictors of skull base recurrence. Postoperative radiation therapy reduced the actuarial probability of skull base recurrence from 15% to 5% (P = 0.03). The crude rates of skull base recurrence were 6% (2/35) and 10% (3/30), respectively, for patients whose skull base were and were not confirmed to be encompassed in the irradiation field. The 5-year overall survival for patients who experienced a skull base recurrence was 19% compared to 91% for those who did not (P < 0.001). Conclusion: The use of postoperative radiation therapy significantly reduced the incidence of skull base recurrence among salivary gland carcinoma patients with perineural invasion.
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