Dynamic magnetic resonance imaging of regional contrast access as an additional prognostic factor in pediatric osteosarcoma

BACKGROUND. The purpose of this article was to evaluate the utility of a ph armacokinetically modeled measure of regional contrast access, based on dyn amic contrast-enhanced magnetic resonance imaging (MRI) studies after preop erative chemotherapy, as a predictor of disease free survival in osteosarco ma. METHODS. The kinetic parameters of a two-compartment pharmacokinetic model of MRI contrast agent accumulation were analyzed in relation to disease fre e survival in 31 patients who received protocol-based therapy for nonmetasr atic osteosarcoma of the extremities. The modeled exchange rate of contrast between the plasma and the tumor extravascular extracellular fluid space s erved as a measure of regional contrast access. The prognostic impact of bo th the clinically accepted standard of histologic evaluation of tumor necro sis and the regional contrast access were analyzed with tumor size as an in fluential factor. RESULTS. Although the histologic grade of response was not a statistically significant prognostic factor in these patients (P = 0.884), regional contr ast access after preoperative chemotherapy was significantly predictive of disease free survival (P = 0.035) in the Cox proportional hazards model. Lo wer regional access before surgery and smaller tumor size were associated w ith a better treatment outcome. Log-rank analyses of Kaplan-Meier curves in dicated that the impact of regional access was most pronounced in patients with larger tumors (P = 0.052). Higher regional access at presentation also was associated significantly with greater decreases during therapy. CONCLUSIONS. Dynamic MRI estimates of regional contrast access after preope rative chemotherapy, when combined with tumor size, holds promise for the e arly identification of patients at risk of recurrence. The availability of such response predictors could facilitate the development of risk-adapted t reatment approaches. (C) 2001 American Cancer Society.