Osteosarcoma: relation between extent of marrow infiltration on CT and frequency of lung metastases

Thirty-seven patients with osteosarcoma were evaluated by CT of both the involved bone and the lungs. The ratio of the extent (E) of the involved marrow segment to the length (L) of involved bone (E/L) was correlated with the presence and subsequent development of pulmonary metastases. The marrow was evaluated by CT for the presence of tumor by measuring mean attenuation coefficients on serial axial scans. Three patient groups were identified: group 1 consisted of seven patients with lung metastases at presentation (mean E/L = 61%), group 2 consisted of 10 patients who developed lung metastases or recurrent tumor either during or after chemotherapy (mean E/L = 39%), and group 3 consisted of 20 patients who completed therapy and remained disease-free (mean E/L = 28%). All patients received chemotherapy in addition to surgical resection except for two patients in group 1. No patient with an E/L ratio greater than 50% remained disease-free for more than 14 months after the initial diagnosis. Fifty percent or greater involvement of the marrow cavity thus carries a particularly poor prognosis, and its absence or presence can be used as a significant prognostic aid in osteosarcoma.