Dosimetric comparison of postoperative interstitial high-dose-rate brachytherapy and modern external beam radiotherapy modalities in tongue and floor of the mouth tumours in terms of doses to critical organs

Örs Ferenczi; Tibor Major; Georgina Fröhlich; Dalma Béla; Szabolcs Tódor; Csaba Polgár; Hironori Akiyama; Botond Bukovszky; Zoltán Takácsi-Nagy

doi:10.2478/raon-2023-0050

Dosimetric comparison of postoperative interstitial high-dose-rate brachytherapy and modern external beam radiotherapy modalities in tongue and floor of the mouth tumours in terms of doses to critical organs

Radiol Oncol. 2023 Nov 30;57(4):516-523. doi: 10.2478/raon-2023-0050. eCollection 2023 Dec 1.

Authors

Örs Ferenczi¹, Tibor Major^{1

2

3}, Georgina Fröhlich^{1

4}, Dalma Béla¹, Szabolcs Tódor¹, Csaba Polgár^{1

2

3}, Hironori Akiyama⁵, Botond Bukovszky^{1

2

6}, Zoltán Takácsi-Nagy^{1

2

3}

Affiliations

¹ Centre of Radiotherapy, National Institute of Oncology, Budapest, Hungary.
² Department of Oncology, Semmelweis University, Budapest, Hungary.
³ National Tumour Biology Laboratory, National Institute of Oncology, Budapest, Hungary.
⁴ Eötvös Loránd University, Faculty of Science, Budapest, Hungary.
⁵ Department of Oral Radiology, Osaka Dental University, Osaka, Japan.
⁶ Department of Oral Diagnostics, Semmelweis University, Budapest, Hungary.

Abstract

Background: The aim of the study was to dosimetrically compare interstitial high-dose-rate (HDR) brachytherapy (BT) and modern external beam radiotherapy modalities, as volumetric modulated arc therapy (VMAT) and stereotactic radiotherapy with Cyberknife (CK) of tumours of the tongue and floor of the mouth in terms of dose to the critical organs.

Patients and methods: In National Institute of Oncology, Budapest, between March 2013 and August 2022 twenty patients (11 male/9 female) with stage T1-3N0M0 tongue (n = 14) and floor of mouth (n = 6) tumours received postoperative radiotherapy because of close/positive surgical margin and/or lymphovascular and/or perineural invasion. High-dose-rate interstitial brachytherapy applying flexible plastic catheters with a total dose of 15 × 3 Gy was used for treatment. In addition to BT plans VMAT and stereotactic CK plans were also made in all cases, using the same fractionation scheme and dose prescription. As for the organs at risk, the doses to the mandible, the ipsilateral and the contralateral salivary glands were compared.

Results: The mean volume of the planning target volume (PTV) was 12.5 cm³, 26.5 cm³ and 17.5 cm³ in BT, VMAT and CK techniques, respectively, due to different safety margin protocols. The dose to the mandible was the most favourable with BT, as for the salivary glands (parotid and submandibular) the CK technique resulted in the lowest dose. The highest dose to the critical organs was observed with the VMAT technique. The mean values of D_2cm3 and D_0.1cm3 for the critical organs were as follows for BT, VMAT and CK plans: 47.4% and 73.9%, 92.2% and 101.8%, 68.4% and 92.3% for the mandible, 4.8% and 6.7%, 7.3% and 13.8%, 2.3% and 5.1% for the ipsilateral parotid gland, 3.5% and 4.9%, 6.8% and 10.9%, 1.5% and 3.3% for the contralateral parotid gland, 7.3% and 9.4%, 9.0% and 14.3%, 3.6% and 5.6% for the contralateral submandibular gland.

Conclusions: The present results confirm that BT, despite being an invasive technique, is dosimetrically clearly beneficial in the treatment of oral cavity tumours and is a modality worth considering when applying radiotherapy, not only as definitive treatment, but also postoperatively. The use of the CK in the head and neck region requires further investigation.

Keywords: HDR; VMAT; brachytherapy; cyberknife; dosimetry; floor of mouth tumour; stereotactic; tongue tumour.

MeSH terms

Brachytherapy* / methods
Female
Humans
Male
Mouth Neoplasms* / radiotherapy
Mouth Neoplasms* / surgery
Organs at Risk
Radiotherapy Dosage
Radiotherapy Planning, Computer-Assisted / methods
Tongue