Cytostatic effects in osteosarcomas as detected by flow cytometric DNA analysis after preoperative chemotherapy according to the COSS 80/82 protocol.

A total of 20 highly malignant osteosarcomas were studied by DNA flow cytometry after preoperative chemotherapy according to the COSS 80/82 protocol to assess their nuclear DNA content and the impact of chemotherapy on DNA ploidy and proliferation. Of the cases studied, 70% revealed aneuploid DNA stem lines with a median value of 1.67, and a median S-phase proportion of 16.1%. These data differed substantially from the results of a preceding study on untreated osteosarcomas revealing a higher frequency of DNA aneuploidy, higher DNA indices, and higher proportions of cells in S-phase. The pretreated tumors also showed a distinct relation between DNA content and the grade of tumor regression. No aneuploid DNA stem line was found in the responder group-I, whereas group-V (osteosarcomas with more than 50% viable tumor tissue) consisted almost completely of aneuploid DNA populations; all tumors with more than 2 DNA aneuploids were found in the latter group. All populations with a DNA index (DI) over 2.0 were found in the nonresponder groups IV and V, where all DNA aneuploids had an S-phase above 12%. No differences in DNA ploidy or proliferation were found in the various histological subtypes of pretreated osteosarcomas. These data indicate that flow cytometric DNA measurement in osteosarcoma may not only serve as a tumor marker, but also support the evaluation of morphologically established regression grades, thereby verifying the patient's prognosis: a high DI (over 2.0), a high number of DNA aneuploids (more than 2), and a high proliferation (S-phase above 12%) seemed to indicate a poor regression of the primary lesion, which may offer a pretherapeutic way of prognostic evaluation.