The present patient had a T3b RCC without metastasis to other organs and was scheduled for surgery. However, his cancer progressed so rapidly that we considered that the risks of systemic spread and adverse perioperative events were unacceptably high and instituted neoadjuvant therapy. Having determined by biopsy that the tumor was an RCC and in light of published reports of the efficacy of a combination of nivolumab plus ipilimumab against these tumors, we chose this combination for our patient.

Nivolumab, an anti-programmed death receptor-1 antibody, exerts its antitumor effect by inhibiting binding between programmed death receptor-1 expressed on T cells and the corresponding ligands (PD-L1) expressed on tumors. Ipilimumab is a monoclonal antibody against cytotoxic T lymphocyte antigen-4 (CTLA-4), which is known to inhibit binding of CD80 and CD86 molecules on antigen-presenting cells, thereby causing proliferation and activation of T cells and promoting presentation of tumor antigen [2]. The phase III CheckMate 214 trial on patients with International Metastatic Renal Cell Carcinoma Database Consortium category intermediate-/poor-risk renal cell carcinoma showed that nivolumab plus ipilimumab achieved significantly longer overall survival and higher objective response rates than did sunitinib alone [3]. In addition, the combination of nivolumab plus ipilimumab reportedly achieves better outcomes in patients with strong PD-L1 expression. Furthermore, it has been reported that PD-L1 expression is strong in sarcomatoid RCC [4]. Survival benefit in patients with sarcomatoid RCC treated with nivolumab plus ipilimumab has recently been reported [5]. Other reports showed while exploratory analysis demonstrated similar response to immune checkpoint inhibitor plus vascular endothelial growth factor receptor—tyrosine kinase inhibitor in the sarcomatoid subgroup than in those without sarcomatoid RCC, post hoc analysis of CheckMate 214 demonstrated an improved response rate for combination of nivolumab plus ipilimumab in patients with sarcomatoid differentiation than in those without [6]. Furthermore, this patient had only tolerable symptoms and was not in urgent situation, and wanted a cure because of absent of distant metastasis. We selected nivolumab plus ipilimumab for our patient on the basis of these reports and the tumor size decreased markedly. Some studies have found that the combination of nivolumab plus ipilimumab can achieve regression of VTT [7,8,9,10]. It can, therefore, be expected that this combination may be so effective that it makes curative surgery for sarcomatoid RCC with IVC-VTT, which is otherwise difficult to operate on, possible. Additionally, the combination of nivolumab plus ipilimumab can reportedly achieve durable responses. However, there is a risk of immune-related adverse effects and no clear criteria for when to proceed with surgery. The optimal use of systemic treatment preceding resection of a primary tumor has not yet been adequately studied. We look forward to accumulation of cases and data from prospective studies.

There have been several reports of patients with metastatic RCC with IVC-VTT that shrank with the combination of nivolumab and ipilimumab, enabling cytoreductive nephrectomy [7,8,9,10]. There have also been two reported cases of complete resection of RCC with VTT without metastasis [11, 12]. However, to our knowledge, there have been no reported cases of successful combination therapy with nivolumab plus ipilimumab for sarcomatoid RCC with IVC-VTT. We, therefore, believe that this is the first reported case of RARN with level II IVCTT after neoadjuvant nivolumab plus ipilimumab. Nephrectomy requiring IVC-VTT often requires liver mobilization and the use of cardiopulmonary bypass, which increases the risk of perioperative complications and death [13]. Robot-assisted surgery enables reliable, shake-free procedures under a clear, magnified field of view with high image quality. It can, therefore, achieve less blood loss and reduce the risk of complications compared with conventional open surgery [14]. In the present case, robot-assisted surgery achieved little blood loss and the planned procedure was completed safely. We expect it will be more widely used in the future.

In conclusion, in our patient, a combination of nivolumab plus ipilimumab for sarcomatoid renal cell carcinoma with IVC-VTT resulted in tumor shrinkage. This enabled complete resection of the tumor by RARN with IVCTT, reducing surgical risks, such as blood loss and perioperative complications.