Re-Irradiation With Proton Beam Therapy for Localized Perineural Spread Following Presacral Recurrence in Sigmoid Colon Cancer: A Case Report.

This report describes the effective management of localized perineural spread (PNS) to the sacral peripheral nerves following a presacral recurrence of colon cancer using proton beam therapy (PBT). The patient, a male in his 60s with a history of sigmoid colon cancer treated with laparoscopic Hartmann's procedure, presented with presacral recurrence two years post-surgery. Radical resection was deemed infeasible, leading to a combined treatment of PBT (75 Gy relative biological effectiveness (RBE) in 25 fractions) and capecitabine. However, three years post-PBT, magnetic resonance imaging revealed swelling of the left S2 nerve with abnormal fluorodeoxyglucose uptake, indicating localized PNS. Re-irradiation with PBT (75 Gy RBE in 25 fractions) was conducted, carefully considering the overlap with the previous PBT field and aiming to minimize dosage to adjacent organs. At 1.5 years post-reirradiation, the patient remained free of recurrence. This case underscores the potential efficacy of PBT and emphasizes the need for further research to assess its broader applicability in comparable situations.