NEAR TETRAPLOID PROSTATE CARCINOMA - METHODOLOGIC AND PROGNOSTIC ASPECTS

BACKGROUND. The clinical value of DNA ploidy analysis in prostate carc inoma has been an issue for investigation for more than 2 decades. In general, diploid or pseudodiploid tumors are associated with a favorab le prognosis and aneuploid tumors with an unfavorable prognosis, irres pective of type of treatment. Turners with DNA values in the tetraploi d region (around 4c) present a diagnostic problem. Such DNA distributi ons may clearly represent aneuploid tumors with an unfavorable prognos is. However, a 4c distribution may conversely represent a tetraploid t umor (possibly a polyploid variant of the diploid tumor) with a favora ble prognosis. Previous data from our laboratory indicate the existenc e of such a tetraploid subgroup. The goal of the current study was to investigate the diagnostic problem of 4c tumors in greater detail. MET HODS. Ploidy classification of cytologic smears by image cytometry was performed in a retrospective study of 334 patients with hormonally tr eated prostate carcinoma. Follow-up time was 30 years or until death. RESULTS. Three ploidy types were defined: near-diploid (D type), near- tetraploid (T type), and highly aneuploid (A type). Tumors with a moda l value within the tetraploid region were found in 27% (92 cases) of t he total material. Of these, 9% were defined as T type and 18% as A ty pe. Overall, 37% of the tumors were classified as D type, 9% as T type , and 54% as A type. Of the A type tumors, one-third had modal DNA val ues in the tetraploid (4c) region. Multivariate analysis showed a stat istically significant difference between A type tumors and D and T typ e, but not between D type and T type. Both D and T type tumors progres sed slowly and killed the patients 5 to 30 years after diagnosis, wher eas A type tumors progressed rapidly and killed the patients within 6 years of diagnosis. CONCLUSIONS. By image cytometry, prostate carcinom a can be divided into three ploidy types: D, T, and A type. Biological ly, however, the tumors fall into only two groups: low grade malignant , pseudodiploid tumors of D or T type, and high grade malignant, highl y aneuploid tumors of A type. (C) 1996 American Cancer Society.