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

Daishi Ichioka, Koji Kawai, Ken Tanaka, Ryutaro Ishitsuka, Takayuki Yoshino, Tomokazu Kimura, Shuya Kandori, Takashi Kawahara, Takahiro Kojima, Joichi Usui, Kunihiro Yamagata, Jun Miyazaki, Hiroyuki Nishiyama

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. 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 m(2). Also, urinary beta2-microglobulin and albumin concentrations in spot urine specimens were measured. The mean eGFRcreat was significantly lower than eGFRcys, at 67.9 and 95.2 ml/min/1.73 m(2), 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 m(2) and eGFRcys ≥60 ml/min/1.73 m(2). 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 m(2) and eGFRcys ≥60 ml/min/1.73 m(2) showed significant beta2-microglobulinuria: a higher prevalence than that in patients with both eGFRs ≥60 ml/min/1.73 m(2). Also, the incidence of microalbuminuria tended to be high in those patients. The present study suggests that eGFRcys may overestimate renal function in TC survivors cured by cisplatin-based chemotherapy.