Diagnosis and tumor response in osteosarcoma and Ewing's sarcoma.

Both osteosarcoma and Ewingʼs sarcoma are highly malignant tumors, usually affecting children and adolescents. Before chemotherapy was introduced in the treatment of these tumors the prognosis was poor, but by intensified pre- and postoperative chemotherapy regimens the prognosis has improved dramatically. It soon became obvious that the tumor response to preoperative chemotherapy also served as a prognostic marker and today the postoperative chemotherapy treatment modality is based on the response rate. Those with a good tumor response receive a less intensive postoperative treatment than those whose tumor response has been poor (Picci 1997 et al., Bacci 2000 et al.). The Scandinavian sarcoma group (SSG), has since 25 years carried out several studies on both osteosarcoma and Ewingʼs sarcoma, some of them in collaboration with the Italian sarcoma group (ISG). The protocols for osteosarcoma SSG II, SSG VIII, ISG/SSG I, ISG/SSG II and SSG XIV, as well as the protocols for Ewingʼs sarcoma SSG IV, SSG IX, ISG/SSG III and ISG/SSG IV are described elsewhere (http://www.ssg-org.net/). In these protocols different methods of assessing the chemotherapy response have been used. Here, we will present and discuss the different methods.