title: FDG PET is superior to CT in the prediction of viable tumour in post-chemotherapy seminoma residuals.
abstract: OBJECTIVE
  In advanced seminoma the management of residuals after completion of chemotherapy is controversial. Some centres routinely perform surgery for lesions > or =3 cm diameter, others recommend surgery solely if the residual fail to shrink or show even growth. This study prospectively investigates whether FDG PET can improve the prediction of viable tumour in post-chemotherapy seminoma residuals.
  
  
  METHODS
  After an expansion of a previous study population, 54 patients from eight centres with metastatic seminoma and a CT-documented mass after chemotherapy were included in the study. Six patients were excluded from evaluation because of protocol violations. After PET, the patients underwent either surgery or were followed clinically. On follow-up the lesions were considered to be non-viable when there was unequivocal shrinking, or when the lesion remained morphologically stable for at least 24 months. Any lesion growth was assumed to be malignant. PET results were compared to CT discrimination (< or > or =3 cm) of the residual masses.
  
  
  RESULTS
  Fifty-two PET scans were evaluable. After adequate chemotherapy, there were 74 CT-documented residual masses ranging in size from 1 to 11 cm (median, 2.2 cm). Their dignities were confirmed histologically in 13 lesions, or by follow-up CT in 61 lesions. Four of forty-seven lesions <3 cm and 11/27 lesions > or =3 cm were viable. PET was true positive in one lesion <3 cm and in 11 lesions > or =3 cm, false negative in three lesions <3 cm, and true negative in 59 lesions (43 lesions <3 cm). No PET scan was false positive. In detecting viability the sensitivity and specificity was 73% (95% CI, 44-88), and 73% (59-83), respectively, for CT (< or > or =3 cm); and 80% (51-95), and 100% (93-100), respectively, for PET (specificity, P < 0.001).
  
  
  CONCLUSIONS
  In post-chemotherapy seminoma residuals, a positive PET is highly predictive for the presence of viable tumour. The specificity of PET is significantly higher than that of CT when using a > or =3 cm cut-off. A negative PET scan is excellent for the exclusion of disease in lesions > or =3 cm, with a somewhat higher sensitivity than CT (n.s.). PET can contribute to the management of residual seminoma lesions, especially in terms of avoiding unnecessary additional treatment for patients with lesions > or =3 cm.
authors.affiliation: Department of Nuclear Medicine, Ludwig Boltzmann Institute for Nuclear Medicine, University of Vienna, Währinger Gürtel 18-20, Vienna A-1090, Austria. alexander.becherer@mediuniwien.ac.at
authors.forename: Alexander
authors.initials: A
authors.lastname: Becherer
authors.forename: Maria
authors.initials: M
authors.lastname: De Santis
authors.forename: Georgios
authors.initials: G
authors.lastname: Karanikas
authors.forename: Monica
authors.initials: M
authors.lastname: Szabó
authors.forename: Carsten
authors.initials: C
authors.lastname: Bokemeyer
authors.forename: Bernhard M
authors.initials: BM
authors.lastname: Dohmen
authors.forename: Jörg
authors.initials: J
authors.lastname: Pont
authors.forename: Robert
authors.initials: R
authors.lastname: Dudczak
authors.forename: Christian
authors.initials: C
authors.lastname: Dittrich
authors.forename: Kurt
authors.initials: K
authors.lastname: Kletter
mesh_terms: D000005:Abdomen / Q000000981:diagnostic imaging; D000328:Adult; D019788:Fluorodeoxyglucose F18; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D018365:Neoplasm, Residual; D049268:Positron-Emission Tomography / Q000379:methods*; D011237:Predictive Value of Tests; D011446:Prospective Studies; D011856:Radiographic Image Enhancement / Q000379:methods; D011860:Radiography, Abdominal / Q000379:methods; D013902:Radiography, Thoracic / Q000379:methods; D019275:Radiopharmaceuticals; D018239:Seminoma / Q000175:diagnosis* / Q000188:drug therapy; D012680:Sensitivity and Specificity; D013736:Testicular Neoplasms / Q000175:diagnosis* / Q000188:drug therapy; D013909:Thorax / Q000000981:diagnostic imaging; D036542:Tomography, Spiral Computed / Q000379:methods*
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18