Cathepsin B and L and stefin A and B levels as serum tumor markers in squamous cell carcinoma of the head and neck.

Cysteine proteinases cathepsin (Cath) B and L and their endogenous inhibitors stefin (Stef) A and B concentrations were measured using a quantitative immunosorbent assay (ELISA; KRKA d.d., Novo mesto, Slovenia) in serum samples from 35 patients with primary and 7 patients with recurrent squamous cell carcinoma of the head and neck (SCCHN), obtained at diagnosis (Serum no.1) and after therapy (Serum no. 2), and compared to sera from 30 (Stef B, 90) healthy volunteers. A significantly higher Stef A (P = 0.005) and lower Stef B (P < 0.001) concentrations were measured in patients' Serum no.1 than in controls, and the levels of Caths B and L and Stef A were found to be significantly elevated in Serum no.1 as compared to Serum no. 2 (P = 0.045, P = 0.041 and P = 0.024, respectively). The time of Serum no.2 collection did not influence the concentration of either Caths or Stefs in these samples, and no correlation was observed with the established prognostic factors for any of the parameters studied. Patients with subsequently diagnosed recurrent disease had a significantly lower Cath L concentration than those without evidence of relapse during follow up (P = 0.05). The risk of disease recurrence and SCCHN-related death correlated significantly with low Cath L serum levels (P = 0.012, P = 0.006). The serum levels of Cath B, Stef A and Stef B did not influence significantly the probability of survival.