Impact of NK cell count on bladder cancer recurrence.

Purpose: The aim of the present study was to evaluate the prognostic value of the local NK cell count in patients with recurrent non-muscle-invasive bladder cancer.

Methods: The archival paraffin-embedded primary tumor specimens were derived from retrospectively-selected patients, who were treated between 1996 and 2001 for bladder cancer. The study group consisted of 46 patients who developed recurrent disease during their first two post-operative years. The control group consisted of 27 patients who did not develop recurrent disease during their first two post-operative years. Specimens were assessed immunohistochemically with standard "ABC" technique. The frequency of NK cells was expressed as total number, estimated for each tumor by counting the positive NK cells in 10 high-power representative fields. Statistical analysis was done using Kruskal-Wallis test.

Results: Patients with recurrent non-muscle invasive bladder cancer in general have significantly higher values of stromal NK cell count than the control group. Patients with single tumor and smaller tumors show a statistically significant difference in NK cell count between study and control group. There also exists a statistically significant difference in stromal NK cell count in patients with clinical stage Ta tumor.

Conclusions: Our results confirm an association of the bladder wall NK cell count in bladder cancer patients with the natural history of disease. Further well-performed, reproducible, large, prospective investigation stratified by clinical parameters, such as tumor number and diameter, is needed to display the true value of this marker in the clinical work-up of bladder cancer patients.