Efficacy of nivolumab plus ipilimumab as first-line therapy for primary tumors in patients with renal cell carcinoma

Objectives: With the emergence of several effective combination therapies, information on their effects at the primary site will be crucial for planning future cytoreductive nephrectomy (CN). The present study focused exclusively on changes in primary tumor sizes following treatment with nivolumab plus ipilimumab and investigated the clinical factors associated with a good response in primary tumors.

Methods and materials: We retrospectively assessed 27 patients diagnosed with advanced renal cell carcinoma (RCC) who started treatment with nivolumab plus ipilimumab. Changes in tumor sizes at the primary site were described using waterfall and spider plots, respectively. We analyzed the correlation of tumor shrinkage between primary and metastatic site. The parameters analyzed between responders and non-responders according to primary tumor sizes were International Metastatic Renal Cell Carcinoma Database Consortium (IMDC) risk scores, peripheral blood markers, and CRP.

Results: The median age and follow-up period were 66 years and 9.3 months, respectively. The median IMDC risk score was 3 (range: 1-6). Nineteen patients were diagnosed with clear-cell RCC (ccRCC) and 8 patients with non-ccRCC. Among ccRCC patients, 9 (47.4%) achieved a significant response with a maximum reduction of 30% or more in the size of the primary tumor from baseline within 4 months, while 3 (37.5%) out of 8 patients with non-ccRCC achieved a significant response. Shrinkage of the primary tumor correlated with the metastatic tumors in both ccRCC and non-ccRCC cases. Of note, 6 patients underwent CN and no viable tumor cells were detected in the surgical specimens of 3 patients whose primary tumors shrank by approximately 50%-60% with a reduction to 4 cm or less. Among ccRCC patients, the neutrophil-to-lymphocyte ratio and monocyte-to-lymphocyte ratio were slightly lower in responders than in non-responders (P = 0.0944 and P = 0.0691). The platelet-to-lymphocyte ratio was significantly lower in responders than in non-responder (P = 0.0391).

Conclusions: Significant responses in primary tumors to nivolumab plus ipilimumab were observed in 50% of ccRCC patients, while responses varied among non-ccRCC patients. Inflammation markers may be predictive factors of treatment responses in primary tumors. Although further studies are needed, the present results suggest the importance of considering CN from radiological and pathological viewpoints.