Brachytherapy Boost for Squamous Cell Carcinoma of the Anal Margin

Abstract

ResumenIntroduction. Anal carcinoma accounts for approximately 2.2% of tumors of the digestive system. Risk factors include human papillomavirus infection and genital warts, smoking and sexual risk behaviors as, high number of sexual partners and being HIVpositive having receptive anal intercourse. Case report A 78 year old woman consulted a dermatologist because of a nonspecific anal discomfort and perianal mass palpation. A biopsy was performed and pathology reported a squamous cell carcinoma. The patient was then referred to the radiation oncology department where staging work-up was done. On physical examination patient had normal sphincter tone and an indurated and ulcerated 2 cm lesion on the left side of the anus. Tumor extended to the external sphincter but it was not infiltrated. A second lesion measuring 0.5 cm was seen on the right-inferior anal verge. Anoscopy showed a 1 cm indurated plaque at 2 cm from the anal verge. Radiotherapy planning was performed with PET-CT that reported an uptake in the anal canal (SUV 10.8). Final stage was cT2N0M0 and after discussing treatment options with a multidisciplinary team, concurrent chemotherapy (5-fluorouracil and mytomicin) and external beam radiotherapy was proposed to preserve anal sphincter function. External beam radiotherapy (EBRT) consisted in 25 fractions of 180cGy (total dose 45Gy) to the anal canal and inguinal, mesorectal, presacral and external and internal iliac lymph nodes. After completing EBRT and chemotherapy patient underwent LDR-brachytherapy boost to the primary lesion. Brachytherapy implant was performed under epidural anesthesia using LDR Iridium 192 wires. A total of 11 wires were implanted with a triangular distribution (Paris-System) using a template. Dose prescription was 30Gy to the 85% of the base isodose, and included the primary lesion as seen before EBRT. Post implant 3D dosimetry was done and implants were removed after 30 hours. Patient was discharged with no complications.http://dx.