ESTRO 2023 - Abstract Book

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ESTRO 2023

Results Using a non-parametric variance analysis (Friedman ANOVA) the mean values of D2(%) and D0.1(%) were as follows for BT, VMAT and stereotaxic planning: mandible D2(%) 51.3% and D0,1(%) 70.0%, ipsilateral parotid gland D2(%) 5.7% and D0,1(%) 9.1%, contralateral parotid gland D2(%) 4.1% and D0,1(%) 7.1%, contralateral submandibular gland D2(%) 7.9% and D0,1(%) 11.6%. The mean extent of the planning target volume (PTV) was 12.5 cm3, 26.6 cm3 and 20.1 cm3 with BT, VMAT and stereotaxic planning, respectively. Conclusion All the three investigated irradiation techniques result in adequate dose distribution in the radiotherapy of operated tongue and floor of the mouth tumors. While the dose coverage of the target volume and the dose in the the mandible were best with BT, in terms of salivary glands, the SRT technique resulted in the lowest dose. The highest dose of critical organs was observed by the VMAT technique. The above results confirm that BT is definitely effective in the treatment of oral cavity tumors and a worth considering modality when using radiation therapy, not only with a definitive intention, but also postoperatively, taking into account its radiobiological advantages known from the literature. 1 Hassan II University Hospital, Radiation Oncology Department, Fes, Morocco; 2 Hassan II University Hospital, Medical Physics Unit, Fes, Morocco Purpose or Objective Introduction : High dose rate skin surface brachytherapy (HDR SS-BT) is a useful non-invasive technique for treatment of skin tumours, with good local control rates as well as excellent cosmetic and functional outcomes. Objective : we report in this study, the experience of the radiation oncology department of the university hospital of Fes Morocco in HDR SS-BT, by describing the technique used and the cases treated. Materials and Methods This is a retrospective study of five cases treated at the radiation oncology department of the University Hospital of FES- MOROCCO, during 4 years (2017-2021). All of our patients had a pathology examination to confirm the diagnosis and a primary treatment. RT was delivered with HDR SS-BT technique with Iridium 192. The application was made by a Catheter Flap Set type applicator by the GammaMed plus machine from VARIAN(figure 1&2). The catheter flap set is designed for treating superficial cancers, and to create a defined space between the source and the tissue, and between the source channels. It’s a highly flexible materials and easily adapted to complex anatomical shapes. The catheter channels are 2 mm in diameter, positioned on the midline of the flap with a 4 mm bolus. The catheter flap is often attached to a thermoplastic mask, to maintain a reproducible position. As for the target volumes; the GTV was the CTV and the PTV was generated from a 0.5cm margin around the CTV respecting the anatomical barriers. The dose prescription varied between 2 schemes depending on the histological type of the primary: 5x6Gy or 3x5Gy, and was prescribed at 3 mm depth. The skin surface dose was constrained to receive a maximum of 135% of the prescribed dose. V90 of the PTV had to be >85%. PO-2191 Technique and oncological outcomes with high dose rate skin surface brachytherapy for skin tumors. K. SOUSSY 1 , M. Ait Erraisse 1 , M. Baraka 2 , W. Hassani 1 , F.Z. Farhane 1 , Z. Alami 1 , T. Bouhafa 1

Results In our study series; we had a variety of pathology treated by this technique and the indication of RT was decided after discussing each case in MDT board: three patients with cutaneous T lymphoma (CTL); classified as T3N0M0 B0, stage IIb; as mycosis fungoid type (MF); received several treatments with no significant response. Brachytherapy was indicated in one case of desmoid tumour given the recurrent nature of the tumour and its superficial location. As for fifth case he presented a keloid scar with numerous recurrences following several treatments involving surgery, laser and bleomycin infiltration. All our patients received treatment according to plan with a daily fraction according to 2 schemes depending on the histological type of the primary. Two of our patients with CTL presented grade III radiodermatitis 15 days after SS-BT, treated with local wound management. With an average 2 years follow-up, all our patients are still alive, with no evidence of disease or recurrence.

Conclusion