Perianal mucinous carcinoma successfully treated with a combination of external beam radiotherapy and high dose rate interstitial brachytherapy.

The case of an 84-year-old man with perianal mucinous carcinoma is presented. The tumour was 6 cm in diameter and extended into the surrounding tissues. Taking the patient's advanced age and disease into account, rectosigmoidectomy and colostomy were carried out without resection of most of the tumour. Radiotherapy consisted of pre-operative external beam radiotherapy (EBRT) of 40 Gy in 20 fractions, post-operative EBRT of 24 Gy in 12 fractions, and high dose rate interstitial brachytherapy of 12 Gy in a single fraction. The patient tolerated the entire course of radiotherapy well. The patient is doing well without regrowth or complications 7 years after radiotherapy. To our knowledge, there have been no reports on the successful outcome of radiotherapy for perianal mucinous carcinoma. This case suggests that a combination of EBRT plus interstitial brachytherapy boost may play a role in the definitive treatment of perianal mucinous carcinoma.