Predictive impact of 2-(18)fluoro-2-deoxy-D-glucose positron emission tomography for residual postchemotherapy masses in patients with bulky seminoma

Purpose: To establish the predictive potential of 2-(18)fluoro-2-deoxy-D-gl ucose positron emission tomography (FDG PET) for detecting viable tumor tis sue in residual postchemotherapy masses of seminoma patients. Patients and Methods: In this prospective multicenter trial, results of FDG PET studies in seminoma patients with postchemotherapy masses greater than or equal to 1 cm were correlated with either the histology of the resected lesion or the clinical outcome on follow-up without resection. Negative PE T scans of residual lesions that were devoid of viable tumor tissue on rese ction or disappeared, shrunk, or remained stable in size for at least 2 yea rs were rated as true-negative (TN). Positive scans without histologic or c linical evidence of tumor tissue were classified as false-positive. In pati ents with histologically positive or progressive lesions, positive PET scan s were defined as true-positive (TP) and negative scans, false-negative (FN ). Results: Thirty-seven PET scans of 33 patients were assessable at a median follow-up time of 23 months (range, 2 to 46 months). Histologic data were a vailable from nine patients who had undergone resection. Twenty-eight patie nts were followed-up clinically and radiologically. Twenty-eight scans were TN, eight were TP, and one was FN. All 14 residual lesions more than 3 cm and 22 (96%) of the 23 less than or equal to 3 cm were correctly predicted by FDG PET. The specificity (100%; 95% confidence interval [CI], 87.7% to 1 00%), sensitivity (89%; 95% Cl, 51.7% to 99.7%), positive predictive value (100%), and the negative predictive value (97%) of FDG PET were superior to data obtained by assessing residual tumor size (less than or equal to or > 3 cm). Conclusion: FDG PET is a clinically useful predictor of viable tumor in pos tchemotherapy residuals of pure seminoma, especially those greater than 3 c m. (C) 2001 by American Society of Clinical Oncology.