Comparative prognostic value of tumor volume in IOIO and IOTKI treatment for metastatic renal cancer

•Tumor size has a higher predictive ability for prognosis in IOIO therapy compared to IOTKI.•Time-dependent AUC analysis shows tumor size consistently predicts PFS and OS in IOIO therapy.•Tumor size outperforms nephrectomy status and IMDC risk classification in IOIO cases.•Tumor size should be a key factor in treatment decisions for mRCC, especially in IOIO therapy. We aimed to investigate the prognostic significance of tumor size in metastatic renal cell carcinoma (mRCC) by comparing the effectiveness of dual immune checkpoint inhibitor (IOIO) and immune checkpoint inhibitor combined with tyrosine kinase inhibitor (IOTKI) therapies. This retrospective observational study included patients with mRCC diagnosed between October 2014 and February 2024 who received IOIO or IOTKI treatment at Kobe University Hospital and 5 affiliated hospitals. Clinical and imaging data were collected, and target lesions were measured according to RECIST v.1.1 criteria. Time-dependent ROC curve analysis was performed to evaluate the prognostic value of tumor size, nephrectomy status, and IMDC risk criteria for progression-free survival (PFS) and overall survival (OS). The study included 180 mRCC patients, consisting of 99 receiving IOIO therapy and 81 receiving IOTKI therapy. Time-dependent AUC analysis showed that tumor size had a higher predictive ability for PFS and OS in the IOIO group than the IOTKI group. In multivariate analysis, tumor size was a significant independent prognostic factor for PFS (HR: 1.010, 95% CI: 1.004–1.016, P < 0.001) in the IOIO group. Moreover, the AUC for tumor size was consistently superior in predicting outcomes compared to nephrectomy status and IMDC risk classification in the IOIO group. Kaplan-Meier curves indicated that tumor size effectively stratified PFS in both nephrectomized and non-nephrectomized cases. Tumor size significantly impacts the prognosis of mRCC patients treated with IOIO therapy, demonstrating greater predictive ability than nephrectomy status and IMDC risk classification. These findings suggest that tumor volume should be considered a critical factor in treatment decision-making for renal cancer, particularly in patients undergoing IOIO therapy.