MIB-1 IMMUNOHISTOCHEMISTRY IN CLINICAL STAGE-I NONSEMINOMATOUS TESTICULAR GERM-CELL TUMORS PREDICTS PATIENTS AT LOW-RISK FOR METASTASIS

BACKGROUND, The clinical Stage I of nonseminomatous germ cell tumors ( NSGCT) is inaccurate in 30% of patients. In previous studies on tumor biologic risk factors, low tumor proliferation rates predicted a group of patients at low risk for occult metastatic disease. The goal of th is study was to confirm the immunohistochemical assessment of tumor pr oliferation using MIB-1 (Ki-67 receptor) in a different patient cohort with different investigators to prove the method's reliability. METHO DS, Orchiectomy specimens of 78 patients with clinical Stage I NSGCT ( 50 patients with pathologic Stage I and 28 patients with pathologic St age II disease, all patients underwent retroperitoneal lymph node diss ection) were retrospectively analyzed by histopathologic reevaluation and MIB-1 immunostaining. RESULTS, Mean MIB-1 values between the two p athologic stages differed significantly (51.5% MIB-1 positive tumors c ells in pathologic Stage I and 75.1% MIB-1 positive tumor cells in pat hologic Stage II disease; P = 0.02). Using a 70% cutoff value, patholo gic stages were correctly classified in 69% of cases (sensitivity of 8 6%, specificity of 60%, negative predictive value of 88%, and positive predictive value of 55%). Compared with traditional risk factors such as percentage of embryonal carcinoma and vascular invasion, in multiv ariate analysis, MIB-1 was the best predictor of patients at low risk for metastasis. CONCLUSIONS, This study in a different patient populat ion with different investigators confirmed previous results of MIB-1 s taining to predict a group of patients with clinical Stage I NSGCT who were at low risk for metastasis. The method is simple and reproducibl e to improve risk classification in low stage testicular carcinoma. Us ing this technique, a group of patients at very low risk for metastasi s can be identified. [See editorial counterpoint on pages 1641-5 and r eply to counterpoint on page 1646, this issue.] (C) 1997 American Canc er Society.