Examination of Nephrotoxicity in Survivors of Childhood Cancer and Comparison of Methods for Estimating Glomerular Filtration Rate

Objective: Increased survival rates in childhood cancers have led the researchers to focus on long-term side effects and possible risk factors for late nephrotoxicity related to the treatment regimens applied. Our aim is to evaluate drug-induced nephrotoxicity in survivors of childhood cancer and to investigate the compatibility of creatinine clearance with the estimated glomerular filtration rate. Methods: The presence of glomerular and tubular dysfunction has been screened among 59 childhood cancer survivors who had completed their treatment regimens with cisplatin, carboplatin, ifosfamide, and /or high dose methotrexate. Results: The mean age of patients was 10.7±5.5 years (2.5-23), and mean follow-up time was 2.6±2.1 years (0.5-8). Renal dysfunction was detected in 65% of the patients. The most prevalent manifestation of renal dysfunction was decreased glomerular filtration rate (n: 19, 32.2%), and increased urinary β2-microglobulin excretion (n: 12, 20.4%), followed by microalbuminuria (n: 6, 10.1%). Survivors treated with combined chemotherapy regimens (cisplatin, carboplatin, ifosfamide) had significantly lower tubular reabsorption of phosphate than those treated with high dose of methotrexate. The glomerular filtration rate analysis was performed using different methods, and a moderate correlation (r=0.563, p=0.00) was found between estimated glomerular filtration rates calculated according to cystatin-C-based equations and Schwartz formula. Conclusion: Childhood cancer survivors demonstrated a high frequency of renal complications in the current study. We have shown that the calculation of the estimated glomerular filtration rate using the Schwartz formula or cystatin-C-based equations is compatible with the creatinine clearance in this specific patient group. In survivors of childhood cancer who cannot perform 24-hour urine collection, determination of estimated glomerular filtration rate is a more practical approach.