Treatment of metastatic bladder paraganglioma with cadonilimab plus radiotherapy: a case report and literature review.

[BACKGROUND] Bladder paraganglioma (PPGL) is a rare neuroendocrine tumor associated with a lower survival rate compared to paragangliomas originating in other anatomical locations. Surgical resection is still the primary treatment modality for bladder paraganglioma; however, this approach carries a significant risk of malignant metastasis. Once metastasis occurs, therapeutic options become notably limited. The response rate and 5-year overall survival for bladder paraganglioma treated with cyclophosphamide, vincristine, and dacarbazine (CVD) chemotherapy are relatively low. Recent advancements in tumor immunotherapy, particularly antibodies targeting CTLA-4 and PD-1/PD-L1, have effectively treated various cancers, including neuroendocrine tumors. These immunotherapeutic approaches offer promising alternatives and potentially improve outcomes for patients with metastatic bladder paraganglioma.

[CASE DESCRIPTION] A 44-year-old male presented with intermittent hematuria, abdominal pain, and frequent urination. Pre-operative computed tomography (CT) revealed a neuroendocrine tumor and a laparoscopic partial cystectomy was subsequently performed. Post-operative pathology confirmed paraganglioma of the bladder, with immunohistochemical results showing SYN (+), P504S (+/-), and Ki-67 (+20%). The patient's post-operative symptoms resolved, returning to normal. However, recurrence occurred 33 months post-surgery. The patient later received 11 cycles of cadonilimab and local radiation therapy, with tumor progression evaluated via imaging every 2 months. During the follow-up period, the patient maintained stable disease for 12 months. After local progression, the patient received targeted therapy, chemotherapy, and palliative treatment. Survival time after recurrence is 25 months. Overall survival from diagnosis is 58 months.

[CONCLUSIONS] We report, for the first time, a case of metastatic bladder paraganglioma in which a patient treated with cadonilimab in combination with radiotherapy maintained stable disease for 12 months. These results demonstrate that this combination therapy may be a potential treatment option for bladder paraganglioma.