An increase in splenic volume after first-line immunotherapy is associated with worse PFS in patients with metastatic renal cell carcinoma

IMPORTANCE: Reliable prognostic markers for immune checkpoint inhibitor (ICI) response in metastatic renal cell carcinoma (mRCC) remain limited. OBJECTIVE: To examine the impact of splenic volume change after ICI initiation on progression-free survival (PFS) and overall survival (OS) in patients with mRCC. DESIGN: A retrospective cohort study reviewing data from 2015 to 2023. SETTING: The Emory Kidney Cancer database (single-center academic instution). PARTICIPANTS: Patients with mRCC who underwent first-line ICI treatment and had available abdominal imaging 30 days before and 60-120 days after ICI initiation. A total of 109 patients met inclusion criteria. EXPOSURE: Splenic volume change calculated as a percentage difference between baseline and follow-up imaging (median 2.8 months post-initiation) using a standardized formula, grouped into ≥10% increase and