Purpose: The prognosis for patients with metastatic renal cell carcinoma (RCC) has markedly improved with the advent of molecular targeted agents and immune checkpoint inhibitors. However, few studies have reported the outcomes of systemic therapy in metastatic RCC patients undergoing dialysis. This study aimed to evaluate the clinical outcomes of systemic therapy for metastatic RCC patients on dialysis. Materials and Methods: We retrospectively reviewed 253 patients with metastatic RCC (17 on dialysis and 236 not on dialysis) who received systemic therapy at Keio University Hospital in Japan. Progression-free survival (PFS), overall survival (OS), and cancer-specific survival (CSS) were assessed using the Kaplan-Meier method. Results: Clear cell RCC was diagnosed pathologically in 52.9% of dialysis patients and 82.6% of nondialysis patients (p=0.007). Among dialysis patients, 58.8% were classified as intermediate risk and 41.2% as poor risk. Regarding first-line therapy, 4 dialysis patients received cytokine therapy, 11 received tyrosine kinase inhibitors, 1 received mammalian target of rapamycin inhibitors, and 1 received immune checkpoint inhibitors. The median PFS (6.9 months, p<0.001), OS (21.2 months, p=0.001), and CSS (29.1 months, p=0.003) were all significantly shorter in dialysis patients. After propensity score matching, no significant difference was observed in PFS. However, significant differences persisted in OS and CSS between the dialysis and nondialysis groups. Conclusion Both OS and CSS were significantly shorter in dialysis patients with metastatic RCC compared to those not on dialysis.

　　Neuroendocrine small cell carcinoma is very rare in comparison with carcinoma of the cervix. In addition, it causes quite often metastasizes and has high recurrence rates. Furthermore, the mortality rate is high even among patients with early stage disease treated with common chemotherapy.　　We described a recurrent case of neuroendocrine small cell carcinoma, in which radiation therapy was delivered successfully but the disease relapsed during postoperative chemotherapy.