Possible abscopal effect in urothelial carcinoma of the upper urinary tract after treatment with immune checkpoint inhibitors

INTRODUCTION: Regression of non‐irradiated metastatic lesions after radiation therapy is known as the abscopal effect. We report a case of urothelial carcinoma in which the abscopal effect was possibly observed after immune checkpoint inhibitor administration. CASE PRESENTATION: A 68‐year‐old woman diagnosed with left renal pelvic cancer underwent total nephroureterectomy and regional lymph node dissection. Eight months later, imaging studies detected local recurrence and paraaortic lymph node metastasis. The tumor progressed despite cisplatin + gemcitabine, pembrolizumab, and gemcitabine + docetaxel therapy. Radiation therapy was administered to a painful back lesion, which resulted in dramatic symptom relief. Computed tomography 2 months after radiation therapy indicated reduced size of the irradiated lesion and some non‐irradiated lymph nodes. CONCLUSION: Combined radiation therapy and immune checkpoint inhibitors can provide additional benefits for certain cancers, possibly due to negative immunomodulatory response blockade. Thus, this combined therapy may be a new metastatic urothelial carcinoma treatment strategy.