Degree of tumor necrosis after neoadjuvant chemotherapy

Most treatment protocols for osteosarcoma use an initial period of systemic chemotherapy before definitive resection of the primary tumor (or resection of sites of metastases). The pathologist assesses necrosis in the resected tumor. Patients with at least 90% necrosis in the primary tumor after induction chemotherapy have a better prognosis than do patients with less necrosis.[30] Patients with less necrosis (<90%) in the primary tumor after initial chemotherapy have a higher rate of recurrence within the first 2 years than do patients with a more favorable amount of necrosis (≥90%).[43]

Less necrosis should not be interpreted to mean that chemotherapy has been ineffective. Cure rates for patients with little or no necrosis after induction chemotherapy are much higher than cure rates for patients who receive no chemotherapy. The EFS rate for patients who receive no adjuvant chemotherapy is approximately 11%.[44] Many large published series of patients treated with chemotherapy have reported EFS rates of 40% to 50% for patients with little or no necrosis in the primary tumor after initial systemic chemotherapy.[45-47] A review of two consecutive prospective trials performed by the Children’s Oncology Group showed that histological necrosis in the primary tumor after initial chemotherapy was affected by the duration and intensity of the initial period of chemotherapy. More necrosis was associated with better outcome in both trials, but the magnitude of the difference between patients with more and less necrosis was diminished with a longer and more intensive period of initial chemotherapy.[48][Level of evidence B1]