Differential treatment responses to immune checkpoint inhibitor (ICI) therapy in a case of multiple primary malignancies: the programmed death ligand-1 (PD-L1) negative ureteral and lung metastasis from a clear cell renal cell carcinoma appearing after robotic-assisted partial nephrectomy progressed after ICI therapy, while synchronous PD-L1-positive primary lung squamous cell carcinoma responded very well to ICI therapy: a case report

Background: Renal cell carcinoma (RCC) and non-small cell lung cancer (NSCLC) are representative malignancies that respond well to immune checkpoint inhibitors (ICIs). Research has been conducted to identify biomarkers, such as programmed death ligand-1 (PD-L1), that would allow the response to ICI therapy to be predicted; however, the complex tumor immune system consisting of both host and tumor factors may also exert an influence. Case presentation: Computed tomographic imaging (CT) incidentally revealed a left renal mass, and a left pulmonary nodule with multiple lymph node metastases (LNMs). Firstly, video-assisted thoracic surgery revealed a lung tumor invading the chest wall. Histologically, the findings of the tumor were consistent with squamous cell carcinoma (SCC), and immunohistochemistry (IHC) showed positive PD-L1 expression. The renal tumor was excised by robotic-assisted partial nephrectomy (RAPN). Histologically, the renal tumor showed the features of clear cell carcinoma (CCC). Four months after the RAPN, CT revealed left hydronephrosis caused by an enhancing ureteral tumor. Then, multiple right lung metastases appeared, and the left lung tumor increased. Following treatment including atezolizumab, the primary lung SCC and the multiple LNMs almost disappeared completely, while the ureteral and right lung metastases showed progression. The ureteral metastasis was resected by left open nephroureterectomy. Histology of the ureteral tumor revealed features consistent with CCC. Histological examination of the multiple right lung metastases that were resected by partial lobectomy via a small thoracic incision also revealed features consistent with CCC. Two months after nephroureterectomy, a solitary left lung metastasis was treated by nivolumab and ipilimumab. Six months after nephroureterectomy, the patient died of RCC. Further studies of specimens revealed that the tumor cells in the primary RCC and the ureteral and lung metastases showed negative results of IHC for PD-L1. Conclusions: The responses to ICI therapy of concomitant RCC and NSCLC were quite different. The PD-L1 expression status in individual tumors in cases of multiple primary malignancies (MPMs) may directly predict the response of each malignancy to ICI therapy, because the host immune system, which may affect the response to ICI therapy, could be the same in MPMs.