2736 - Institutional Experience with Interstitial and Surface Mold Brachytherapy for Head and Neck Cancers: Efficacy, Toxicity, and Clinical Outcomes

Purpose/Objective(s): To assess the efficacy, toxicity, and clinical outcomes of interstitial and surface mold brachytherapy in patients with head and neck cancers.

Materials/Methods: Between 2021 and 2025, 20 patients with T1-T2/N0 primary or recurrent head and neck cancers were treated with High dose rate (HDR) ¹⁹²Ir interstitial and surface mold brachytherapy. Of these, 17 had squamous cell carcinoma (SCC) and 3 had basal cell carcinoma (BCC). Catheter placement was performed using free-hand technique, followed by CT-based planning. The prescribed dose was individualized based on tumor size, treatment intent (primary, re-irradiation, or adjuvant), and proximity to critical structures. 8(40%) and 12(60%) cases were treated using mold and interstitial brachytherapy respectively.The most frequently used fractionation schedule was 4 Gy per fraction, delivered twice daily over 11 fractions, with a median total biologically effective dose (BED) of 63.5 Gy. A cumulative BED of up to 122 Gy was administered in cases requiring salvage re-irradiation.

Results: The median age was 66 years (range:32-87), with 17 males and 3 females. Tumor distribution included 12 cases of oral cavity, 2 cases of oropharynx and 6 cases of cutaneous malignancies of head neck region. According to AJCC staging, 6 cases were T1 and 14 were T2, with a median tumor size of 2.6 cm (range: 1.5–4) and median tumor volume of 3.4 cc (range: 0.75–14.7 cc). Average 6 catheters were used (range: 3–10). Six patients received salvage re-irradiation, with a median time to re-irradiation of 32.5 months (range: 13–121 months). Treatment was well tolerated, with 75% experiencing RTOG Grade II and 25% developing Grade III acute toxicity, managed conservatively. At a median follow-up of 9 months (range 3-42 months), local control rates was 80%. 13 out of 14 patients in the primary cohort were disease free and 1 patient required salvage surgery. In the recurrent cohort, 5/6 patients succumbed to disease progression either locally (3) or metastatic progression (2).

Conclusion: This study demonstrates that interstitial and surface mold brachytherapy is a viable treatment option for select head and neck cancer patients, providing effective local control with acceptable toxicity. These findings support its role in organ preservation and salvage strategies, warranting further studies to assess long-term functional outcomes and patient-reported quality of life.