Efficacy of low-dose rate brachytherapy utilizing a mold with gold-198 grains for hard palate and gingival cancer

Sep 30, 2026

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Objectives: Evaluate Au-mold therapy using gold-198 grains for patients with hard palate and gingival cancer, focusing on treatment outcomes and feasibility. Methods: A retrospective review analyzed 37 cases treated with Au-mold therapy alone, assessing outcomes, complications, and simulating dose distribution with clinically available calculation systems. Results: Primary cases showed a 5-year local control rate around 80%, with poorer control in recurrent cases; severe oral mucositis and late complications were uncommon. Conclusions: Findings support Au-mold therapy as a potential option and motivate strategies to further improve efficacy.

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Oral Radiology (2026) 42:197–203 [https://doi.org/10.1007/s1](https://doi.org/10.1007/s1) 1282-025-00853-y Efficacy of low‑dose rate brachytherapy utilizing a mold with gold‑198 grains for hard palate and gingival cancer Hitomi Nojima1 · Atsushi Kaida1 · Mihoko Haraguchi2 · Mai Murase2 · Mariko Hattori2 · HirofumiTomioka3 · Hiroyuki Harada3 · Ryoichi Yoshimura4 · Masahiko Miura1 Received: 16 May 2025 / Accepted: 12 August 2025 / Published online: 25 August 2025 © The Author(s) 2025 Abstract Objectives Mold therapy using gold-198 grains (Au-mold therapy) is a radical treatment for early stage oral cancer owing to its localized delivery of radiation. Understanding the efficacy and limitations of Au-mold therapy is crucial for optimizing treatment protocols and enhancing outcomes. Thus, this study evaluated the treatment outcomes of Au-mold therapy inpatients with hard palate and gingival cancer and assessed its feasibility as a therapeutic modality. Methods This retrospective study analyzed data from 37 cases with hard palate and gingival cancer who received Au-mold therapy alone. Treatment outcomes and complications were evaluated, and the dose distribution of Au-mold therapy was simulated using clinically available calculation systems. Results A notable 5-year local control rate of approximately 80% was noted in primary cases, whereas recurrent cases exhibited lower local control rates. Severe oral mucositis was not observed, and late complications, such as osteoradionecrosis and oral ulceration, were infrequent following Au-mold therapy. Conclusions This study provides insights into the use of Au-mold therapy for oral cancer. Promising outcomes in primary cases suggest its potential as a treatment option. Future research should focus on innovative strategies to enhance the efficacy of Au-mold therapy in oral cancer management. Keywords Oral cancer · Brachytherapy · Gold-198 grain · Mold therapy · Dose simulation * Atsushi Kaida[kai.mdth@tmd.ac.jp](kai.mdth@tmd.ac.jp) * Masahiko Miura [masa.mdth@tmd.ac.jp](masa.mdth@tmd.ac.jp) 1 Department of Dental Radiology and Radiation Oncology, Graduate School of Medical and Dental Sciences, Institute of Science Tokyo, 1-5-45 Yushima, Bunkyo-Ku, Tokyo 113-8549, Japan 2 Department of Advanced Prosthodontics, Graduate School of Medical and Dental Sciences, Institute of Science Tokyo, Tokyo, Japan 3 Department of Oral and Maxillofacial Surgical Oncology, Graduate School of Medical and Dental Sciences, Institute of Science Tokyo, Tokyo, Japan 4 Department of Radiation Therapeutics and Oncology, Graduate School of Medical and Dental Sciences, Institute of Science Tokyo, 1-5-45 Yushima, Bunkyo-Ku, Tokyo 113-8549, Japan Introduction Low-dose-rate brachytherapy (LDR-BRT) is an effective treatment for early stage oral cancer [1–3] . In Japan, two primary sources are used for LDR-BRT: grain-shaped gold- 198 (Au-198; Fig. 1a), which is suitable for most oral cavity sites, and iridium-192 (Ir-192) pins, which have extensive applications in mobile tongue cancer. Typically, Au-198 grains are directly implanted into tumor tissues under local anesthesia, enabling localized high-dose administration within a week. However, for tumors of the hard palate and gingiva, direct insertion is difficult due to the thickness of the mucosa and presence of bone. Consequently, an alternative approach involves irradiation using a mold resembling a denture, particularly for hard palate and gingival cancers [3] . A customized mold (Fig. 1b) was crafted for each patient, wherein Au-198 grains were embedded (Au-mold), and radiotherapy was administered for approximately 5 d. While isolation is necessary during Au-mold therapy to prevent Fig. 1 Photos of Au-198 grains (a) and a mold (b) . Ten Au-198 grains (pink) are embedded with paraffin wax and autopolymerizing resin in this mold radiation exposure to others, the procedure is minimally invasive and imposes little physical burden on p

FAQs

What is Au-mold therapy and why is it used for hard palate and gingival cancer?

Au-mold therapy delivers localized radiation using gold-198 grains embedded in a patient-specific mold. It is used because direct implantation into hard palate and gingiva is difficult due to mucosal thickness and bone.

How was the study designed and what patient cohort was analyzed?

The study was retrospective and included 37 cases of stage I–II squamous cell carcinoma of the hard palate and upper or lower gingiva. All cases received Au-mold therapy alone.

What treatment outcomes and complications were observed?

Primary cases achieved an approximately 80% 5-year local control rate, while recurrent cases had lower local control. Severe oral mucositis was not observed, and late complications like osteoradionecrosis and oral ulceration were infrequent.

Sep 30, 2026

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