Tanisha Nagar
Wellington Blood and Cancer Centre
Radiation Therapist

Shelley Pearson
Radiation Therapist - Brachytherapy Supervisor
Wellington Blood and Cancer Centre

Dean Paterson
Radiation Therapist - Head of Treatment
Wellington Blood and Cancer Centre

Nichola Naidoo
Radiation Oncologist
Wellington Blood and Cancer Centre

Delivery of radiation treatment to widespread superficial disease of the extremities can pose a number of technical challenges with conventional megavoltage external beam radiation therapy, superficial x-ray therapy or electron beam therapy due to the large treatment area, complex skin contours and disease that is often circumferential. At our institution, surface mould brachytherapy is considered for local palliation of patients with widespread areas of in-transit melanoma metastases that cannot be easily excised.

A 54 year-old male with stable stage IV in-transit melanoma was referred to our institution for consideration of high dose rate (HDR) surface mould brachytherapy. The intended treatment site was the circumference of the patients right upper leg from above the knee extending superiorly to include the right buttock, the resultant surface area was 1941.5cm2. The available surface mould materials in our institution at the time were not suitable due to the irregular contour of the treatment area. Silicone bolus was recently commissioned for external beam radiation therapy at our institution and was utilised to create a custom surface mould brachytherapy applicator for the treatment of this patients’ right upper leg and buttock.

Applicator construction required multiple patient visits to assess the conformity of the mould at various stages of construction. Plastic tip catheters were taped on with inter-catheter spacing of between 1 – 1.8cm. A vacuum bag was made to aid patient positioning and a CT scan was performed with the applicator in place. Treatment was planned and delivered in two sections to minimise the impact of side effects for the patient with a planned break to allow for healing. The prescribed dose for section one was 30Gy in five fractions, two fractions per week and section two was 30Gy in six fractions, two fractions per week to a depth of 0.5cm.

Treatment was well tolerated with grade one erythema at the completion of each section. The custom applicator was a viable solution that was safely developed by the multi-disciplinary team using equipment readily available in our department.

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