2713 - Rethinking Whole Tongue Radiation for Oral Tongue Squamous Cell Carcinoma
Presenter(s)
A. K. Bennett1, K. W. Qualls1, Y. Garces1, D. K. Ebner1, W. S. Harmsen2, D. M. Routman1, M. A. Neben-Wittich1, D. J. Ma1, J. M. Wilson1, T. D. Malouff1, S. H. Patel3, L. A. McGee3, A. L. Holtzman4, H. Mohammadi4, A. Amundson1, K. Price5, D. L. Price6, and S. C. Lester1; 1Department of Radiation Oncology, Mayo Clinic, Rochester, MN, 2Department of Biostatistics and Health Sciences Research, Mayo Clinic, Rochester, MN, 3Department of Radiation Oncology, Mayo Clinic, Phoenix, AZ, 4Department of Radiation Oncology, Mayo Clinic, Jacksonville, FL, 5Department of Medical Oncology, Mayo Clinic, Rochester, MN, 6Department of Otolaryngology-Head and Neck Surgery, Mayo Clinic, Rochester, MN
Purpose/Objective(s): Postoperative radiotherapy (PORT) for oral tongue squamous cell carcinoma (OTSCC) standardly includes treatment of the whole tongue (WT). Advances in treatment delivery enable partial tongue (PT) treatment. Herein we report the clinical outcomes of PT radiation at our institution.
Materials/Methods: This was an IRB-approved retrospective review of patients with a diagnosis of OTSCC treated from 2014 to 2022 excluding patients treated on clinical trials. All patients received curative-intent standard fractionation PORT +/- chemotherapy (CRT) including bilateral neck RT. Treatment of WT or PT (defined as < 80% of the residual tongue in the CTV) was at the discretion of the treating physician. The cumulative incidence (CI) of local recurrence (LR), regional recurrence (RR), and distant recurrence (DR) were calculated, with death as a competing risk. Univariate and multivariate cox models compared patient and treatment related factors. Local control was estimated using Kaplan-Meier analysis. Physician-reported CTCAEv4.0 scores and patient-reported EORTCHN35 surveys were collected at standard timepoints for a subset of patients.
Results: 71 patients were included with a median follow up of 61.2 months (IQR 40.8-90). 22 patients (31.0%) had primary closure and 49 patients (69.0%) had flap reconstruction. 18 patients (25%) were treated with PT and 53 (74.6%) were treated with WT. Pathologic T stages included T1/2 38 patients (53.5%; PT 34.2%, WT 65.8%) and T3/4 33 patients (46.5%; PT 15.2%, WT 84.8%). Multivariable analysis showed no significant differences in LR by pTstage (pT1/2 vs pT3/4), use of concurrent CRT, surgical closure, and PT vs WT. 27 patients (38.0%) received concurrent CRT. 2 year local control was 76.9% for PT and 71.4% for WT (p = 0.678). Of the 18 patients (25.4%) with LR, 13 (72.2%) had a simultaneous RR and/or DR. 4 patients (22.2%) treated with PT and 14 (26.4%) treated WT had a tongue recurrence (p = 0.402). All PT local failures occurred within the radiation field. Dose to the mandible was significantly reduced with PT radiation. The median mandible V50Gy was 50% (IQR 40%-60%) for PT and 70% (IQR 60%-80%) for WT (p < 0.0001) and the median mandible V60Gy was 10% (IQR 10%-20%) for PT and 30% (IQR 20%-40%) for WT (p < 0.0001). The mean oral cavity dose was numerically lower for PT but was not statistically significant (40.9 Gy vs 44.1 Gy, p = 0.1191). Patients who received PT radiation had a lower CI of physician-reported acute grade 3+ toxicity scores for swallowing, oral health, and skin changes and improved grade 2+ tongue function. There were no recorded late grade 3+ toxicities for PT radiation; however, there were late grade 3+ toxicities in swallowing, oral health, and skin changes for WT radiation. There were no significant differences in EORTCHN35 scores between WT and PT.
Conclusion: PT radiation was not associated with any marginal recurrences, yielded a high rate of tongue control, lower doses to the mandible, and favorable toxicity.