3732 - Interstitial Brachytherapy in Early-Stage Oral Cavity Carcinomas

A. Sharma¹, A. Aashita², Y. I. K N², T. Choden³, A. Ghosh¹, A. Dagar¹, K. Kamboj¹, S. Mallick⁴, J. Sharma¹, N. Gupta², A. Mishra², S. Panda², A. Kumar², R. Kumar², K. Sikka², A. Thakar⁵, and D. Sharma⁶; ¹National Cancer Institute, All India Institute of Medical Sciences, New Delhi, India, ²National Cancer Institute, AIIMS-Jhajjar, Jhajjar, India, ³All India Institute of Medical Sciences, New Delhi, India, ⁴National Cancer Institute, Jhajjar, Haryana, India, ⁵All India institute of Medical Sciences, New Delhi, India, ⁶All India Institute of Medical Sciences, New Delhi, New Delhi, India

Purpose/Objective(s): Brachytherapy is one of the most conformal forms of radiation delivery. To our knowledge this is one of the largest and most recent cohorts available in the world on use interstitial high-dose rate (HDR) brachytherapy for early stage oral cavity carcinomas (OCC). We herein present the dosemetric and clinical outcomes of OCC patients treated with HDR brachytherapy. Materials/

Methods: Patients of early stage OCC subjected to interstitial brachytherapy between May 2020 to December 2023 were included in the present study. Brachytherapy was performed either in radical or adjuvant setting. All patients were discussed in multidisciplinary tumor board where conjoint decision and treatment option were discussed by team compromising of radiation oncologists, head and neck surgeons, surgical oncologists and medical oncologists. In a radical setting all patients were subjected to combination of EBRT +brachytherapy boost. EBRT to elective neck was 45Gy in 20 fractions or 50/50.4 Gy in 25/28 fractions. Patients with radiologically positive lymph nodes were subjected to SIB-IMRT of 56.26-58.25 Gy in 25 fractions (< 1cm nodes) or 63 or 65 Gy in 28 fractions to the involved nodes (> 1cm). The dose of brachytherapy boost was 21Gy/24Gy in 7-8 fraction. Double plane implant was performed in all patients (square or triangular geometry). Adjuvant brachytherapy was delivered to a dose of 40Gy/10 fractions (close margins) & 44Gy-48Gy in 11-12 fractions (positive margins). Dosemetric parameter evaluated in the study included V200, V150 & V100. Dose non uniformity ratio (DNR) was calculated as V150/V100. Locoregional control and overall survival was calculated in all patients.
Results: The study included 58 patients of OCC. Majority 68% of lesion were located in anterior tongue & buccal mucosa (16%). Most patients had T2 lesion (72%), T1 disease was present in 22% patients & remaining were T3 lesions. Majority (67%) were subjected to radical treatment & 33% to adjuvant brachytherapy. Median catheter placement was 8 catheters (range 5-11 catheters). Median V200 was 3.1cc (range 1.5-6.1cc), V150 median was 6.9cc (range 3.6-12.7cc) & V100 median was 25.8 cc (range 12.5-45.8cc). Median DNR was 0.26 (range 0.22-0.43). At a median follow up of 22 months (range 3 -40 months), 41 patients were alive whereas 17 patients were dead (14 cancer mortality, 03 non cancer mortality). Seven patients experienced regional recurrence (5 isolated and 2 locoregional) & 3 patients developed distant metastases. The 1- & 2-year local control (LC) in adjuvant brachytherapy was 75% & 72% respectively. The 1- & 2-year LC in radical setting was 79% & 77% respectively.
Conclusion: HDR brachytherapy is good treatment option for OCC patients in radical & adjuvant setting. Our results demonstrated LC of 77% at 2 years in radical setting. Interstitial brachytherapy should be offered as treatment option by all multidisciplinary tumor boards especially for patients willing for organ preservation.