Superficial High Dose Rate Brachytherapy for the Treatment of Lower Eyelid Carcinomas

Abstract

Basal and Squamous cell carcinomas of the eyelid account for a large proportion of skin cancers. Historically the eyelid has been a challenging area to successfully treat and achieve good cosmetic outcomes for patients. This work aims to establish a new way to treat lower eyelid basal and squamous cell carcinomas by using an intraluminal catheter and a high dose rate iridium brachytherapy source. Different mould techniques were used to place the catheter under the lower eyelid, with the aid of a stereotactic head phantom. The optimal mould was then scanned, and a treatment plan was established using Oncentra Brachytherapy software, in combination with the AAPM TG43 algorithm for dose. Two methods were used to verify this plan. Gafchromic film was placed under the mould and analysed using FilmQA Pro software. For organs at risk, optically stimulated luminescence dosimeters were used for point doses and read out using microstarii software. Different setups involving varying levels of bolus around the catheter were tested to eliminate the air gaps to remove the uncertainty of density differences. The results showed that an effective treatment plan can be created using an intraluminal catheter and 6 mm of bolus between the skin and catheter to produce an appropriate dose distribution in the patient for the GEC-ESTRO recommended fractionation scheme of 4 Gy per fraction, with a total of 10–12 fractions, 3 times a week for a total dose 40–48 Gy.