Decreased expression of KAI1 metastasis suppressor gene is a recurrence predictor in primary pTa and pT1 urothelial bladder carcinoma.

OBJECTIVE: To examine the expression of the KAI1 metastasis suppressor gene and to evaluate its relationship with tumor recurrence in primary pTa and pT1 urothelial bladder carcinoma.

METHODS: Samples were obtained from 87 patients after transurethral resection (TUR). Tumor stage and grade were reviewed in 33 patients with pTa and in 54 patients with pT1, with a mean follow-up time of 47.4 +/- 30.1 months. The KAI1 protein immunohistochemical assay was performed. Prognosis was analyzed using the Kaplan-Meier method and Cox's proportional hazards model. Correlation between KAI1 expression and recurrence according to each clinicopathological factor was comparatively evaluated using the chi-squared test.

RESULTS: Decreased expression of KAI1 protein failed to reach statistical significance for stage (P = 0.25) or morphology of tumor stem (P = 0.19), but it was significantly related to tumor size (P = 0.016). The recurrence-free 5-year survival rates of the group with decreased KAI1 expression was 69.7%, which was significantly higher than the 22.2% for the KAI1-positive group (P < 0.0001). In univariate and multivariate analyses, decreased expression of KAI1 protein, stage pT1, tumor size >3 cm and sessile tumors were independent prognosis factors of recurrence. Despite the lower recurrence rate expected by considering only the clinicopathological factors, decreased KAI1 expression was able to identify the group with a high risk of recurrence.

CONCLUSIONS: Downregulated KAI1 expression in bladder tumors tends to relate to stage and morphology of the tumor stem and was significantly correlated to tumor size. Decreased expression of KAI1 was associated with the degree of invasiveness and progression of the cancer and was an independent prognostic factor of recurrence in primary pTa and pT1 urothelial bladder carcinoma.