Table 2 Summary of tumor markers in dialysis patients (modified from [31])

Free PSA (fPSA) could be filtered through glomeruli, consistent with its low molecular weight (28 kDa). Decreased GFR leads to an increased serum level of fPSA and higher percent fPSA to tPSA (%fPSA), since the level of tPSA does not differ compared with that of the controls [35]. Although not eliminated by low-flux membranes, fPSA is cleared by high-flux membranes [76], since molecules smaller than 5 and 50 kDa are filtered by low-flux and high-flux dialysis membranes, respectively [39].

CA-125 is elevated in patients with peritoneal, pleural, or pericardial effusion [37]. In particular, CA-125 is falsely elevated as a result of nonspecific peritoneal irritation or peritonitis in patients undergoing peritoneal dialysis [38]. The serum concentration of CA-125 is increased during hemodialysis, probably due to hemoconcentration [32].

Although the metabolism and clearance are not fully understood, previous studies revealed that the serum levels of CA19-9, CEA, SCC, and NSE are elevated in dialysis patients compared with patients with normal renal function [39–42]. An increase in the serum levels of these tumor markers is also found during hemodialysis, probably as a result of hemoconcentration [32]. It should be noted that SCC is cleared by high-flux membranes due to its molecular weight of 42 to 48 kDa, although it is not eliminated by low-flux membranes [33].