A case of neoadjuvant chemotherapy-resistant muscle-invasive bladder cancer that markedly responded to pembrolizumab before conversion radical cystectomy.

INTRODUCTION: Recently, perioperative use of immune checkpoint inhibitors has improved the prognosis of muscle-invasive bladder cancer. It is unclear whether radical cystectomy or systemic pembrolizumab is the optimal next treatment in patients with muscle-invasive bladder cancer and progressive disease in the pelvic lymph node following neoadjuvant chemotherapy (NAC).

CASE PRESENTATION: A 62-year-old woman with cT3N0M0 bladder cancer and high programmed death-ligand 1 expression developed solitary obturator lymph node metastasis following 5 cycles of neoadjuvant chemotherapy. Six subsequent cycles of pembrolizumab shrank the lymph node significantly, and conversion radical cystectomy was planned. Pathologically, only carcinoma in situ around the scar of transurethral resection of bladder tumor remained in the primary tumor, and the accumulation of foamy macrophages and fibrosis without viable tumor cells was observed in the dissected lymph node. Eighteen months passed without a recurrence following radical cystectomy.

CONCLUSION: Pembrolizumab administration before radical cystectomy achieved a good response in a patient with obturator lymph node metastasis following neoadjuvant chemotherapy.