ABSTRACT
To determine the histological response to preoperative chemotherapy of the percentage of tumor necrosis, and to assess the relationship between the histological response and the oncological result. Eighty patients with osteosarcoma were managed with preoperative and postoperative chemotherapy and operative resection at Shafa Yahyaeeyan Hospital, Tehran, Iran between 2003-2005. Sections of each operative specimen were examined, and the histological response to chemotherapy was graded. Grade 1 indicated necrosis of 50% of the tumor or less; grade 2, necrosis of more than 50% yet less than 90 percent; grade 3, necrosis of more than 90 percent. The mean duration of the follow-up of the surviving patients, who were continuously free from disease was 1044 days. The histological response to preoperative chemotherapy [p=0.016] was the most important predictor of event-free survival. The rate of event-free short-term survival for the 80 patients entering this study was 86 percent [69 patients] at 12 months, 50% 24 patients at 24 months, and 21% [5 patients] at 40 months, with 5 patients surviving for a median of 1096 days. The histological response to preoperative chemotherapy is an important clinical predictor of the result of operative treatment of osteosarcoma. This indicator should be used to identify patients who are at high risk for metastasis, as such patients may be candidates for more intensive or novel therapy