Pitfalls of Using the Cockcroft-Gault Formula When Calculating Carboplatin Dose for the Adjuvant Treatment of Patients with Stage i Seminoma

ABSTRACT Introduction Single dose Carboplatin (C) AUC7 (7 x glomerular filtration rate (GFR) mls/min + 25) is a standard adjuvant treatment option for patients with stage I seminoma. Measuring GFR by a nuclear medicine method represents the gold standard, but is not available in all centres. 24h urine collection may be prone to sampling errors. Estimating GFR by the Cockroft-Gault formula (CG) is popular amongst oncologists but data supporting its use in this situation is limited. Reduction of C dose by 10% in the adjuvant treatment of seminoma stage I is associated with a trend for higher relapse rate. Methods Data from 202 consecutive, male patients (median age 39, range 23-68 years) with stage I seminoma with complete documentation of GFR by TC99m DTPA, serum-creatinine, age, height and weight were evaluated. Actual C doses (ACD) based on GFR measurement by TC99m DTPA were compared with estimated C doses (ECD) based on GFR estimation using CG formula. Differences between the ACD and ECD were correlated to age and body mass index (BMI) using Fisher's Exact test, Pearson correlation and linear regression. Results 202 patients were included in the correlation analysis and 181 patients in the comparison of different subgroups, respectively. Lower BMI and higher age were significantly associated with lower ECD, Pearson correlation coefficients 0.59 (p Discussion CG significantly underestimates GFR in leaner and older patients. According to our data over a third of patients with BMI 20–25 or aged 41–50 would be at risk for undertreatment if CG were used routinely. Physicans need to be aware of these limitations when using CG to calculate C dose in patients with stage I seminoma. Disclosure All authors have declared no conflicts of interest. Table: 857P Age (years) 90-110% ACD >110% ACD BMI (kg/m2) 90-110% ACD >110% ACD 21-30 n = 29 14% 4 72% 21 14% 4 20-25 n = 60 35% 21 57% 34 8% 5 31-40 n = 84 14% 12 68% 57 18% 15 25-30 n = 81 21% 17 69% 56 10% 8 41-50 n = 68 40% 27 56% 38 4% 3 30-40 n = 33 15% 5 58% 19 27% 9