Possible risk of overestimation of renal function using cystatin C-based eGFR in testicular cancer survivors treated with cisplatin-based chemotherapy.

BACKGROUND: Chronic kidney disease (CKD) is a major long-term morbidity of testicular cancer (TC) survivors cured by cisplatin-based chemotherapy. We conducted the present study to elucidate the usefulness of cystatin-based estimated glomerular filtration rates (eGFRcys) for diagnosis of CKD compared to creatinine-based eGFR (eGFRcreat) in those patients.

METHODS: eGFRcys and eGFRcreat were measured in 53 TC survivors. The 24-h creatinine clearance (CrCl) was measured in 12 TC survivors and 17 CKD patients with medical disease; all of them had eGFRcreat <60 m/min/1.73 m2 . Also, urinary beta2-microglobulin and albumin concentrations in spot urine specimens were measured.

RESULTS: The mean eGFRcreat was significantly lower than eGFRcys, at 67.9 and 95.2 ml/min/1.73 m2 , respectively (p < 0.05). The prevalence of stage 3-5 CKD differed by GFR estimation methods. It was 47.2% with eGFRcreat and only 7.5% with eGFRcys. There were 21 patients with eGFRcreat <60 ml/min/1.73 m2 and eGFRcys ≥60 ml/min/1.73 m2 . In all 12 TC survivors, the eGFRcys values were higher than both eGFRcreat and GFR (24-h CrCl). In contrast, no difference was observed among eGFR values in the 17 patients with CKD due to medical disease. Ten of 21 patients with eGFRcreat <60 ml/min/1.73 m2 and eGFRcys ≥60 ml/min/1.73 m2 showed significant beta2-microglobulinuria: a higher prevalence than that in patients with both eGFRs ≥60 ml/min/1.73 m2 . Also, the incidence of microalbuminuria tended to be high in those patients.

CONCLUSIONS: The present study suggests that eGFRcys may overestimate renal function in TC survivors cured by cisplatin-based chemotherapy.