CAN MRI PREDICT THE HISTOPATHOLOGICAL RESPONSE IN PATIENTS WITH OSTEOSARCOMA AFTER THE FIRST CYCLE OF CHEMOTHERAPY

The magnetic resonance (MR) changes after one cycle of chemotherapy we re compared with the prechemotherapy studies in 39 patients with osteo sarcoma, in order to identify MR changes which can be used to assess e arly response to chemotherapy. Measurements of total tumour volume, si gnal intensity, and tumour enhancement of the intra- and extraosseous tumour component were performed. Change in the amount of oedema was su bjectively assessed. Changes observed were correlated with histopathol ogical response. Changes in tumour volume and of the signal intensity of the extraosseous tumour component on T2-weighting were the only two parameters which correlated significantly (P < 0.05) with histopathol ogical response. Increase of tumour volume is the most significant par ameter and indicates poor response (sensitivity 89%, specificity 73%). Only one good responder showed increase of tumour volume. Decreased o r stable tumour volume was observed in both good and poor responders. Increase of signal intensity was found exclusively in five poor respon ders (sensitivity 100%, specificity 23%). Decreased or stable signal i ntensity was observed in both good and poor responders. Changes in the amount of oedema and contrast enhancement could not predict response at an early stage. We conclude that increase of tumour volume and incr ease of T2 signal intensity of extraosseous tumour can be predictive f or poor response. MR criteria are not helpful in the early identificat ion of good responders.