Classic Osteogenic Sarcoma Osteogenic sarcoma is the most common primary malignanttumor of bone, making up 20 % of all primary malignancies,with approximately 500-1000 new cases diagnosed each year inthe United States. The classic or most common form of osteo-sarcoma is seen typically in children and young adults, with amale preference. It occurs in the metaphyseal areas of fast growingbones with the most common location being the distal femur,second the proximal tibia, and third the proximal humerus.50% of the lesions will be found around the knee joint. This tumoris rare in in small bones such as the hand or the foot, or in vertebralsegments. Patients usually present with spontaneous symptomsof pain in the area, followed several month later with a tumormass that is usually diagnosed by biopsy within six months afteronset of symptoms. The radiographic appearance of the lesionis typically a permeative lytic lesion seen in the metaphyseal area
of a long bone with cortical breakthrough and periosteal elevationcreating a Codman’s reactive triangle, followed later by a sunburstpattern of chaotic bone formation in the soft tissue outside the peri-osteal sleeve. In a small percentage of cases, a so-called skip lesionwill appear as a separate nodule of tumor activity totally separatefrom the primary lesion which, when found, suggests a very poorprognosis for survival. Fifty percent of osteosarcomas are of theosteoblastic type, but in a smaller percentage of cases, there willbe a prominence of cartilage or fibrous tissue that does not seem toinfluence the prognosis for survival. The staging process for this disease includes a MRI study of theprimary tumor that helps identify soft tissue invasion by the tumorand defines the medullary extent of the tumor which helps theoperating surgeon determine the level of amputation or limbsalvage resection. A bone isotope scan is performed to rule out thepossibility of other bony foci in the skeletal system and a CT scanof the chest is obtained to rule out the possibility of metastatic
disease to the lung. The final staging process includes a biopsyof the primary site performed in such a way as to not contaminatevital structures that might interfere with the potential for a limbsalvage resection at a later date. Prior to 1970, the prognosis for survival with this disease wasonly 20% even though early amputation was performed at a highlevel. Pulmonary metastasis was the reason for a fatal outcome inthese early cases, however, with the advent of multi-drug chemo-therapy the prognosis for survival has now increased to approx-imately 60%. The drugs most commonly used for systemic controlof the disease include high dose methotrexate, adriamycin,cysplatin, and ifosfamide. These drugs are administered througha central venous line on a cyclic basis every three to four weeksfor approximately two months prior to a surgical removal of thetumor. Chemotherapy is then continued for approximately fourmonths after surgical treatment. At the present time, 90% of patients with osteosarcoma are
treated by limb salvage resection. The most common type ofreconstruction consists of a total joint replacement such as arotating hinge at the knee. A smaller group of patients are treatedwith allograft reconstruction or combinations of the above.Excisional arthrodesis was a popular technique many years agobut now patients prefer a reconstruction that involves normaljoint motion. The prognosis for survival is influenced by thedegree of tumor necrosis produced by the preoperative chemo-therapy protocol, so that at the time of surgical resection if thereis more than 90% necrosis of the tumor, the patient has a muchbetter prognosis for survival (approximately 85% at five years).Pulmonary metastasis is still the major concern following treat-ment for osteosarcoma and, if this does occur, aggressive surgicalresection of the lesions thru the chest wall is frequently performed.There is a 30% survival rate at five years following this procedure.As with other forms of cancer, recent molecular genetic studieshave revealed a high incidence of abnormality in the P-53suppressor genes found in this tumor.