Positron Emission Tomography Scans in Postchemotherapy Seminoma Patients With Residual Masses: A Retrospective Review From Indiana University Hospital
Authors: DeQuincy A. Lewis, Mark Tann, Kenneth Kesler, Alan McCool, Richard S. Foster, Lawrence H. Einhorn
Journal: Journal of Clinical Oncology (2006)

TO THE EDITOR: Testicular cancer is highly curable, with 5-year survival rates over 95%. 1 Seminomas usually present as confined to the testis (clinical stage I).Small volume stage II disease (Ͻ 3 cm) is treated with abdominal radiotherapy.Bulky stage II and all stage III disease is treated with cisplatin-based chemotherapy.A confounding issue with seminoma is the evaluation of a postchemotherapy residual mass. 2 This usually represents fibrosis rather than persistent seminoma.Investigators at Memorial Sloan-Kettering (New York, NY) advocate surgery for all residual postchemotherapy masses larger than 3 cm. 3Other centers, including ours, have taken a more conservative approach given the high incidence of fibrosis.We perform serial computed tomography (CT) imaging and only intervene if there is progressive disease. 4ositron emission tomography (PET) scans have been used in an attempt to differentiate between fibrosis and persistent germ cell tumors.With nonseminomatous germ cell cancer, PET scans cannot distinguish fibrosis from teratoma as both are metabolically inert. 5For pure seminoma, where teratoma is not a factor, PET scans have been clinically utilized to predict the histology of residual masses.In the SEMPET trial, PET scans more accurately predicted which persistent lesions represented fibrosis versus persistent seminoma compared withCTscans. 6,7Weretrospectivelyassessedtheaccuracyofpostchemotherapy PET scans in seminoma patients with residual masses.All PET scans were performed a minimum of 6 weeks from completion of chemotherapy in patients with residual postchemotherapy masses.Study was conducted from April 2002 to September 2004.A PET scan was considered true-positive if either the mass in question was proven to represent persistent seminoma by surgical pathology or if the patient clinically progressed.A study was considered falsepositive if surgery done afterwards revealed fibrosis, necrosis, or inflammation.A study was considered true-negative if a patient remained disease free after the negative scan.A study was considered false-negative if a patient had a relapse of disease after a scan was interpreted as negative.Twenty-four PET scans were reviewed from 19 patients who had received primary or salvage chemotherapy for seminoma.Fourteen PET scans were done after primary chemotherapy and 10 were done after salvage treatment.Twelve PET scans were read as negative.None of the patients with negative PET scans have relapsed with seminoma, thus giving PET scans a negative predictive value of 100%.These 12 patients have a median follow-up of 29ϩ months (range, 22ϩ to 38ϩ months).There were 12 PET scans read as positive.PET scans identified all eight patients who had persistent disease after chemotherapy, thus giving them a sensitivity of 100%.However, four positive PET scans led to surgical resections of residual masses revealing only fibro-PET scans are being used more frequently in treatment paradigms for various malignancies.However, as our data show, with respect to residual masses in postchemotherapy seminoma patients, positive PET scans have their limitations and should not be relied on solely to make decisions in this patient population.A negative PET scan indicates a low likelihood of persistent seminoma after chemotherapy.However, a positive PET scan does not translate to a similar high probability of persistent seminoma.