[A Case of Radiation-Induced Lumbosacral Plexopathy after CRT for Rectal Cancer]

A 71-year-old man received preoperative chemoradiotherapy(CRT)for advanced rectal cancer. From just after CRT, a burning sensation appeared on the skin of the outer thighs and buttock. Laparoscopic abdominoperineal resection was performed after CRT. About 2 months after the surgery, weakness of the lower limbs appeared, but the patient was able to walk. About 4 months after the surgery, the patient became unable to walk. MRI examination was performed, but no abnormalities were found. Peripheral nerve electrical examination revealed severe axonopathy. Radiation-induced lumbosacral plexopathy(RILP)was suspected. The patient was able to walk with a cane after treatment with taking medication of mirogabalin and rehabilitation. Peripheral nerve injury caused by treatment for pelvic tumors is called RILP. In Japan, there have been reports of RILP occurring after radiation therapy for cervical cancer, but no reports related to CRT for rectal cancer. It is a serious adverse event as a late effect, and it is important to understand the pathophysiology.