OBJECTIVE: To determine the efficacy of radiotherapy in the local control of Perianal Intraepithelial Neoplasia Grade 3 at a single institution.

PATIENTS AND METHODS: This retrospective case series consists of 30 patients treated with local radiotherapy (RT) at the British Columbia Cancer Agency between 1997 and 2017. Chart review was performed to abstract data on patient and treatment characteristics. Outcomes evaluated were local control and survival.

RESULTS: Of the 30 patients, 5 had local failure, 3 as recurrent in-situ disease, and 2 as invasive disease. Only 1 recurrence occurred before 5 years. Radiotherapy doses ranged from 42.5 – 60 Gy. The actuarial 5 and 10 year local control rates were 96% and 51%, respectively. 3 patients had a treatment break due to acute RT reaction. Of 6 recorded deaths, none was due to anal disease.

CONCLUSIONS: Moderate dose local RT is associated with excellent local control of Perianal Intraepithelial Neoplasia Grade 3 with minimal acute toxicity.