Concurrent Management of Prostate Cancer and Perianal Fistula: A Case Report, Treatment Considerations, and Review of Literature.

Background: Prostate cancer and pre-existing perianal fistula are challenging conditions to manage concurrently as pelvic radiotherapy may raise concern for impaired wound healing, infection, or fistula progression. Although radiotherapy has traditionally raised concern as a risk factor for fistulization, this case suggests that selected patients with a pre-existing perianal fistula may be treated with careful multidisciplinary planning and modern radiotherapy techniques. Case Presentation: A 70-year-old male diagnosed with favorable intermediate-risk prostate cancer and a concurrent perianal fistula was treated with definitive radiation therapy and staged surgical treatment, respectively. The patient underwent intensity-modulated radiation therapy (IMRT) with daily image-guided radiation therapy (IGRT), receiving a total dose of 70 Gy in 28 fractions while minimizing radiation dose to the perianal region. Prior to radiation, a seton was placed to facilitate drainage and reduce infection risk from the fistula. Following radiotherapy, the patient underwent successful surgical fistulectomy without complications. At 26 months posttreatment, the patient remains free of biochemical recurrence and without recurrence of the perianal fistula. Conclusions: This case highlights the clinical importance of applying and coordinating established management principles to an uncommon and challenging scenario. Although seton placement, IMRT/IGRT, and fistula surgery are individually well-established approaches, their sequencing in the setting of localized prostate cancer with a concurrent pre-existing perianal fistula remains poorly described. This report offers a practical example of individualized, staged management in a complex clinical scenario for which standardized treatment pathways remain limited.