Near tetraploid prostate carcinoma. Methodologic and prognostic aspects

Abstract

Background: The clinical value of DNA ploidy analysis in prostate carcinoma has been an issue for investigation for more than 2 decades. In general, diploid or pseudodiploid tumors are associated with a favorable prognosis and aneuploid tumors with an unfavorable prognosis, irrespective of type of treatment. Tumors with DNA values in the tetraploid region (around 4c) present a diagnostic problem. Such DNA distributions may clearly represent aneuploid tumors with an unfavorable prognosis. However, a 4c distribution may conversely represent a tetraploid tumor (possibly a polyploid variant of the diploid tumor) with a favorable prognosis. Previous data from our laboratory indicate the existence of such a tetraploid subgroup. The goal of the current study was to investigate the diagnostic problem of 4c tumors in greater detail.

Methods: Ploidy classification of cytologic smears by image cytometry was performed in a retrospective study of 334 patients with hormonally treated 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 modal value within the tetraploid region were found in 27% (92 cases) of the total material. Of these, 9% were defined as T type and 18% as A type. 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 values in the tetraploid (4c) region. Multivariate analysis showed a statistically significant difference between A type tumors and D and T type, but not between D type and T type. Both D and T type tumors progressed slowly and killed the patients 5 to 30 years after diagnosis, whereas A type tumors progressed rapidly and killed the patients within 6 years of diagnosis.

Conclusions: By image cytometry, prostate carcinoma can be divided into three ploidy types: D, T, and A type. Biologically, however, the tumors fall into only two groups: low grade malignant, pseudodiploid tumors of D or T type, and high grade malignant, highly aneuploid tumors of A type.