Candice Deans
GenesisCare Oncology Queensland
Brachytherapy Services Manager

Holly Stephens
Medical Physics Registrar
GenesisCare Oncology Queensland, Australia/University of Adelaide, South Australia, Australia

David Schlect
Radiation Oncologist
GenesisCare Oncology Queensland, Australia

Tanya Kairn
A/Prof Principal Medical Physicist
Royal Brisbane and Women’s Hospital, Queensland, Australia/Queensland University of Technology, Queensland, Australia

Background Basal and squamous cell carcinomas (BCC and SCC) account for 90% of skin cancers. Of this 90%, approximately 5 to 10% arise in the eye region. Currently surgery is the widespread treatment methodology for these carcinomas, even though the eye region poses some challenges for surgery, namely cosmetic results and tissue recovery. In this study, a new way of treating these carcinomas was developed, using a High Dose Rate Brachytherapy remote afterloader and superficial catheters implanted in a custom mould. This creates a treatment modality that is already associated with positive treatment outcomes and good cosmesis. This method also removed the need to use surgically implanted catheters that were common in previous treatment methods. Methods A Radiation Oncologist outlined clinically realistic treatment areas on a stereotactic head phantom for the lower eyelid region. Several different treatment setups were then evaluated, including using different types and numbers of catheters, mould materials and placements. Specific attention was placed on ensuring the minimisation of air gaps and dosimetric reproducibility. Treatment plans were then created on a CT scan of the phantom using Oncentra Brachytherapy and TG43-U1 dose calculations. The Radiation Oncologist assessed the plan for clinical suitability and approved the dosimetry represented on the stereotactic phantom using a standard dose fractions for non-melanoma skin cancers. After the treatment plan was delivered, 2D dose distributions were analysed using radiochromic film and Film QA pro software, and point doses, especially on the eye lens, were measured using Optically Stimulated Luminescence Dosimeters. Results The treatment plan created using a single intraluminal catheter in a thermoplastic custom mould yielded the best results for coverage and reproducibility of all combinations tested. Measurements of the eye lens dose showed that when using a conventional fractionation scheme the lens dose can be significantly reduced by incorporating an external eye shield and moving the lens superior to the lower eyelid by instructing the patient to ‘look up’ during treatment. Conclusion A clinically viable treatment method has been created using superficial high dose rate brachytherapy for the treatment of lower eyelid BCC and SCC, without the need for invasive surgery. References Manghani J, Kahn K (2016) A study of the role of brachytherapy Ir192 in treatment of eyelid tumors. International Journal of Medical Research and Review 4 Martinez-Monge R, Gomez-Iturriaga A (2007) High-dose-rate brachytherapy in lower eyelid cancer. Brachytherapy 6 (3):227-229

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