News | January 08, 2009

FDG-PET Shows No Advantage Over CT in Predicting Residual Masses

January 8, 2009 – In a study published in the December issue of Journal of Clinical Oncology, results showed that [18F]fluorodeoxyglucose positron emission tomography (FDG-PET) offered no additional value over computed tomography (CT) or tumor marker analysis (TMA) in predicting the histology of residual masses.

The German Multicenter Positron Emission Tomography Study Group evaluated the ability of FDG-PET to predict the tumor histology of residual post-chemotherapy nonseminomatous germ cell tumors (NSGCT), as compared with that of standard approaches using CT and TMA. The results showed that vital carcinoma and mature teratoma were found in 55 percent of residual masses in patients who underwent chemotherapy for NSGCTs in a study, and researchers concluded that FDG-PET provides no additional benefit over conventional diagnostic procedures.

The analysis involved 121 patients with NSGCTs (median age, 30 years) who were enrolled by multiple German centers from 1998 to 2003. The patients had either a primary or a metastatic retroperitoneal tumor that was greater than 5 cm or they had distant metastases (at the time of diagnosis or at first relapse). Eligible patients received cisplatin-based chemotherapy, followed by secondary resection of residual lesions. FDG-PET was performed in all patients before the secondary surgery, but after completion of CT and measurement of alpha fetoprotein (AFP) and beta-human chorionic gonadotropin (beta-HCG) levels.

A positive predictive value of 70 percent was assumed for CT. Positive and negative predictive values of FDG-PET were both estimated to be 90 percent. Thus, an accuracy of 80 percent was required for FDG-PET to demonstrate superiority over CT in terms of distinguishing vital tumors from mature teratomas and necrosis.

The sensitivity and specificity rates for FDG-PET were 70 percent and 48 percent, respectively. Although the sensitivity of FDG-PET was significantly higher than that of TMA analysis (P

FDG-PET imaging offered no additional benefit for patients with either normalized serum tumor markers or markers that were persistently elevated after chemotherapy. False-positive, true-positive, and false- or true-negative results were recorded in 28 percent, 24 percent and 24 percent of patients, respectively. FDG-PET was associated with a higher rate of false-positive results for lesions located in the chest versus the abdomen (41 percent versus 12 percent). A higher rate of false-negative results was observed for lesions located in the retroperitoneum than in the thorax (30 percent vs 5 percent).

Source: J Clin Oncol. 2008 Dec 20;26(36):5930-5935, K Oechsle, M Hartmann, W Brenner, S Venz, L Weissbach, C Franzius, S Kliesch, S Mueller, S Krege, R Heicappell, R Bares, C Bokemeyer, M de Wit

For more information: jco.ascopubs.org

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