MSOR8 Presentation Time: 5:35 PM

Abstract

Purpose

To elucidate systematic approach towards commissioning, implementing and establishing a high dose rate (HDR) interstitial brachytherapy (ISBT) program for head and neck cancers in a new tertiary cancer centre in India.

Materials and Methods

We present the systematic approach and challenges encountered during the implementation of ISBT for head and neck cancers and early outcome of patients treated between September 2020 and September 2022 at our Institution.

Results

In an established infrastructure for high Dose rate Brachytherapy, we explored implementing H & N BT. Joint tumor board discussions, reviewing of existing treatment guidelines and shared decision making with patients helped to start the program. A comprehensive disease mapping was done using clinical drawings (figure 1) & clinical pictures taken before EBRT and BT. Appropriate check list for performing BT procedure, discussions for anaesthesia requirements, dedicated team of Nurse, RTT & Medical physicist, BT planning and dose parameters were reviewed. A successful collaboration with dental surgeon to work on prosthesis especially to spare mandible for high dose regions was established which evolved from using simple rubber catheters, wax to customized acrylic spacers. All suitable patients were either offered radical BT or BT boost after completion of EBRT.A total of 18 patients diagnosed with early-stage oral cancer underwent treatment with ISBT, either as a boost following VMAT (n=13) or 3DCRT (n=2), or as BT Alone (n=3). The primary tumour sites were lateral border of the tongue (n=13), lip (n=3), and buccal mucosa (n=2). The median tumour size was 2 cm, with 13 cases classified as T1 and 5 as T2 with infiltrative lesion in 13 pts and proliferative lesion in remaining 5 pts.Three patients received ISBT alone (1 with buccal mucosa cancer, 2 with lip cancer), while 15 underwent concurrent neck irradiation alongside primary tumour treatment, with a median dose of 50 Gy in 25 fractions over 5 weeks, followed by HDR ISBT after a median gap of 31 days (IQR, 18-34 days). Most patients (n=9,50%) required implantation in two planes, with a median of 11 catheters (range 9-15). The median dose for ISBT boost cases was 22.5Gy in 5 fractions @ 4.5Gy/fraction, while for radical ISBT, it ranged from 40 Gy in 10 fr to 49.5 Gy in 11 fr. The EQD2 was 74 Gy (range: 69-77.5 Gy EQD2), and the median overall treatment time for combined EBRT and ISBT boost was 67 days (range: 47 - 88 days). Mandibular ISBT doses were limited to a median of 4.3 Gy (D 0.1 cc) and 3.15 Gy (D 1cc) per fraction with cumulative dose(Dmax) in EQD2 of 53Gy. The prescribed dose for radical ISBT ranged from 40 to 48 Gy in 10-15 fr.At the last follow-up, grade 1 xerostomia was reported in 38.9% of patients, with none experiencing grade 2 or higher xerostomia. One patient developed osteoradionecrosis of the mandible with minimal exposure of the alveolar bone(Mandibular dose of 81.1 Gy EQD2) . None of the patients experienced > grade 2 speech or swallowing dysfunction, although 5 (27.7%) reported sensitivity to spicy foods. At a median follow-up of 27 months (range, 29 to 35 months), the overall 2-year loco-regional control rate was 78%. Isolated local failure occurred in 5 patients (29.4%), while one patient experienced loco-regional failure and another had combined local and distant (lung metastases) failure. Salvage surgery was performed in four cases, resulting in disease control for 3 patients. One patient declined surgery, and another with distant metastasis received palliative care. The 2-year overall survival rate was 85.2%, with three patients deceased, two due to progressive disease.

Conclusions

A comprehensive multidisciplinary, multimodality team approach resulted in a successful implementation of HDR-ISBT for head & Neck Cancers with initial outcome demonstrating promising clinical outcomes.