Comparison of plasma clearance of [51Cr]CrEDTA based on three, two and single samples to measure the glomerular filtration rate in patients with solid tumors: a prospective cross-sectional analysis Anne C. Gomes; George B. Coura Filho; Luiz A. Gil Junior; Renato A. Caires; Emmanuel A. Burdmann; Carlos A. Buchpiguel; Veronica T. Costa e Silva; Marcelo T. Sapienza;