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Perianal synovial sarcoma treated postoperatively with Iodine-125 brachytherapy: Technical details
Susan Tovey1, Clare Stannard2, Gerrie Maree1
1Department of Medical Physics, Groote Schuur Hospital and University of Cape Town, Cape Town, South Africa.
Purpose:
A 23-year-old lady had an incompletely excised perianal sarcoma. Brachytherapy as the sole treatment, rather than further surgery or external beam radiotherapy, was considered to be the best option with the least morbidity.
Methods And Materials:
Although brachytherapy techniques with iridium-192 for anal and rectal carcinoma are well described using a perianal template, the size of the template was not suitable for a two-plane implant that needed to be in situ for about 4 days. An anal canal applicator was designed, which carried three templates about 15 mm apart inside it, to ensure accurate alignment of the tubes, and an inferior template that was 90 mm from the perianal skin. Three inner and three outer tubes of iodine-125 seeds were designed to treat a 2 o'clock h wedge of perianal tissue as a temporary implant. A thin metal shield was placed around a hole to protect the uninvolved anal canal. The tubes were inserted under general anesthetic and delivered a dose of 59 Gy at 0.8 Gy/h over 75 h. A spinal anesthetic was maintained for the duration of the insertion.
Results:
The treatment was well tolerated, and the patient is well and clear of disease 6 years later with minimal morbidity.
Conclusions:
Iodine-125 is a low-energy isotope, readily available in our unit, that can be easily screened to reduce morbidity to surrounding normal tissues. In the form of seeds, it provides a flexible system that can be adapted to different tumor sites as required, as illustrated in this case.