According to findings from a cross-sectional study, urinary calprotectin cannot be used as a specific tumor marker for bladder cancer (PLoS One. 2019;14[3]:e0213549).

“Urinary calprotectin, a mediator of the innate immune system, has been identified as a biomarker in bladder cancer,” explained Kathrin Bausch, MD, Urological University-Clinic Basel-Liestal, University Hospital Basel, Switzerland, and colleagues, who conducted a prospective study to evaluate the link between sterile leukocyturia and urinary calprotectin in patients with low- and high-grade bladder cancer.

A total of 52 patients with bladder cancer and 40 healthy controls were included in the study, and sterile leukocyturia was defined as >5.0 leukocytes per visual field in absence of bacteriuria.

Patients with low- and high-grade bladder cancer had comparable rates of sterile leukocyturia (60% and 62%, respectively; P = .87). Conversely, Dr Bausch et al found the median absolute urinary leukocyte count to be significantly higher in patients with sterile leukocyturia and high-versus low-grade bladder cancer (P <.01).

In addition, a significant correlation was observed between urinary calprotectin and leucocyte concentration, according to a Spearman correlation (R = 0.4; P <.001). Compared with patients without sterile leukocyturia, the median urinary calprotectin concentration was 4.5 times higher in patients with bladder cancer (P = .03).

“Subgroup analysis revealed a significant difference in urinary calprotectin regarding the presence of sterile leukocyturia in high-grade patients,” Dr Bausch and co-investigators reported.

Furthermore, they found that the leukocyte concentration was the only significant factor impacting urinary calprotectin, according to a multivariate analysis (OR, 3.2; 95% CI 2.5-3.8; P = .001).

Of note, immunohistochemistry showed that patients with high-grade bladder cancer with sterile leukocyturia had calprotectin-positive neutrophils and tumor cells.

“Urinary calprotectin cannot be regarded as a specific tumour marker for bladder cancer, but rather as a surrogate parameter for tumour inflammation,” concluded Dr Bausch and colleagues.—Hina Porcelli