title: Development of a new equation to estimate creatinine clearance in cancer patients.
abstract: OBJECTIVE
  Determining renal function is important for chemotherapy eligibility and dosing. Measured creatinine clearance (mCrCl) is the gold standard but is cumbersome. Equations estimating CrCl (eCrCl) based on serum creatinine (SCr) produce widely varying estimates. Considering that SCr is derived from skeletal muscle, this study prospectively developed a new eCrCl equation in cancer patients using CT-defined muscle surface area (MSA) and evaluated its utility in a separate, retrospective series.
  
  
  METHODS
  In a prospective, observational cohort study of cancer patients, mCrCl by 24-h urine collection was correlated with CT-determined MSA to create an equation for eCrCl [muscle surface area (cm(2)) × 42/SCr]. eCrCl by Wright, Cockcroft-Gault (CG), CKD-EPI, MDRD, and MSA was compared to mCrCl to determine fit. MSA-eCrCl was used to simulate carboplatin dosing in a retrospective series of advanced non-small cell lung cancer (NSCLC).
  
  
  RESULTS
  Prospectively, 22 patients were accrued and evaluable (12 males; median age 69). MSA-eCrCl correlated stronger (r (2) 0.80) than current equations (r (2) 0.47-0.69) with mCrCl. In calculating carboplatin doses for 89 NSCLC patients with MSA and CG-eCrCl, median error of CG-determined carboplatin dose was 5.5 % (range -19.0 to 44.2 %), assuming that MSA was better at estimating CrCl. Forty-two patients (47 %) received doses that varied ≥10 % of what was calculated by MSA.
  
  
  CONCLUSIONS
  We propose a new formula for eCrCl in patients that appears more accurate than current formulae and may have implications for chemotherapy efficacy and toxicity. Studies to validate this formula are under way.
authors.affiliation: Department of Oncology, Cross Cancer Institute, 11560 University Avenue, Edmonton, AB, T6G 1Z2, Canada, mpchu@ualberta.ca.
authors.forename: Michael P
authors.initials: MP
authors.lastname: Chu
authors.forename: Larissa
authors.initials: L
authors.lastname: McCaw
authors.forename: Cynthia
authors.initials: C
authors.lastname: Stretch
authors.forename: Charles
authors.initials: C
authors.lastname: Butts
authors.forename: John
authors.initials: J
authors.lastname: Hanson
authors.forename: Michelle
authors.initials: M
authors.lastname: Kuzma
authors.forename: Vijaya L
authors.initials: VL
authors.lastname: Damaraju
authors.forename: Vickie E
authors.initials: VE
authors.lastname: Baracos
authors.forename: Michael B
authors.initials: MB
authors.lastname: Sawyer
mesh_terms: D000368:Aged; D000970:Antineoplastic Agents / Q000008:administration & dosage; D016190:Carboplatin / Q000008:administration & dosage; D002289:Carcinoma, Non-Small-Cell Lung / Q000097:blood / Q000188:drug therapy / Q000652:urine*; D015331:Cohort Studies; D003404:Creatinine / Q000097:blood / Q000652:urine*; D005260:Female; D005919:Glomerular Filtration Rate / Q000502:physiology; D006801:Humans; D008175:Lung Neoplasms / Q000097:blood / Q000188:drug therapy / Q000652:urine*; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D011446:Prospective Studies; D051437:Renal Insufficiency / Q000097:blood / Q000652:urine*; D012189:Retrospective Studies
chemical_list: D000970:Antineoplastic Agents; D003404:Creatinine; D016190:Carboplatin