Remarkable antitumor effect of nivolumab in a patient with metastatic renal cell carcinoma previously treated with a peptide‐based vaccine

INTRODUCTION: The safety and efficacy of combination therapy comprising immune checkpoint inhibitors and cancer‐specific peptide vaccines have not yet been established. CASE PRESENTATION: A 71‐year‐old female metastatic renal cell carcinoma patient with multiple lung and pleural metastases. She had been treated with interferon alpha, sunitinib, axitinib, and pazopanib sequentially, but no clinical efficacy was observed. She participated in a clinical trial using cancer‐specific peptide vaccine therapy. Initially no antitumor effect was observed, and vaccine therapy was ceased after two courses. But 3 months after the start of nivolumab, remarkable tumor shrinkage was observed at all metastatic sites, which resulted in almost complete response at 6 months. At 10 months, nivolumab was stopped due to cellulitis at the peptide vaccine inoculation site. Intriguingly, even after nivolumab discontinuation, complete response was maintained for more than 1 year. CONCLUSION: We experienced a remarkable antitumor effect by nivolumab in a patient who was previously treated with vaccine therapy.