[Therapy-induced changes in osteosarcoma after neoadjuvant chemotherapy (COSS 86 Therapy Study). Correlation between morphologic findings and clinical follow-up].

207 osteosarcomas were examined morphologically after neoadjuvant chemotherapy according to the COSS-86 protocol using representative slides of one whole tumor plane. The rate of responders 63%. In relapse-free patients both the whole tumors and the vital areas there of were smaller than in patients with relapse during a follow-up period of 5 years. Within the subgroup of osteoblastic osteosarcomas, metastases were observed following smaller tumors than in chondroblastic osteosarcomas. Therefore, in addition to degree of regression, histological subtype and tumor size should be considered in the prognostic evaluation of osteosarcomas.