Purpose: To define the clinical value of 2-18fluoro-deoxy-D-glucose positron emission tomography (FDG PET) as a predictor for viable residual tumor in postchemotherapy seminoma residuals in a prospective multicentric trial.
Patients and methods: FDG PET studies in patients with metastatic pure seminoma who had radiographically defined postchemotherapy residual masses were correlated with either the histology of the resected lesion or the clinical outcome documented by computer tomography (CT), tumor markers, and/or physical examination during follow-up. The size of the residual lesions on CT, either >3 cm or < or =3 cm, was correlated with the presence or absence of viable residual tumor.
Results: Fifty-six FDG PET scans of 51 patients were assessable. All 19 cases with residual lesions >3 cm and 35 (95%) of 37 with residual lesions < or =3 cm were correctly predicted by FDG PET. The specificity, sensitivity, positive predictive value, and negative predictive value of FDG PET were 100% (95% CI, 92% to 100%), 80% (95% CI, 44% to 95%), 100%, and 96%, respectively, versus 74% (95% CI, 58% to 85%), 70% (95% CI, 34% to 90%), 37%, and 92%, respectively, for CT discrimination of the residual tumor by size (>3 cm/< or =3 cm).
Conclusion: This investigation confirms that FDG PET is the best predictor of viable residual tumor in postchemotherapy seminoma residuals and should be used as a standard tool for clinical decision making in this patient group.