Abstract
Upper tract urothelial carcinoma (UTUC) is an uncommon and aggressive malignancy that often presents as an invasive disease. After receiving systemic therapy, stereotactic body radiation therapy (SBRT) offers a non-surgical option for consolidative local tumor control by delivering radiation doses in limited fractions. While SBRT is generally well tolerated in the treatment of UTUC, there is a small but serious risk of radiation-associated complications. We present a case of a 67-year-old male with metastatic UTUC of the renal pelvis treated with chemotherapy and immunotherapy. Due to persistent disease at the primary site, he underwent consolidative SBRT using a PULSAR (Personalized Ultra-fractionated Stereotactic Adaptive Radiotherapy) approach to his left kidney mass. Weeks later, he developed a renocolic fistula that was complicated by sepsis. Despite a diverting colostomy and antibiotics, he re-presented with hemorrhagic shock due to an aortocolonic fistula that required emergent endovascular aortic repair (EVAR). This case illustrates a rare but serious complication of consolidative SBRT in a patient with extensive retroperitoneal malignancy. Multidisciplinary planning and close surveillance are critical to ensuring the safe integration of SBRT in the management of metastatic UTUC.