Positron emission tomography and clinical predictors of survival in primary extragonadal germ cell tumors.

Background: Primary extragonadal germ cell tumors (EGTs) are an uncommon malignancy -accounting for 2-4% of all germ cell neoplasms in adult males. Their prognosis is worse than that for testicular germ cell tumors because of their relative chemoresistance and frequent presentation with widely disseminated metastases. We have studied the role of fluorodeoxyglucose positron emission tomography (FDG-PET) for outcome prediction of patients with EGTs.

Patients And Methods: We have retrospectively analysed 36 men with germ cell tumors originating in the mediastinum or the retroperitoneum. All patients were treated between 1994 and 2010. Negative result of testicular ultrasonographic examination and/or testicular biopsy was required for diagnosis of EGT. Platinum-based systemic therapy was used in all cases, and resectable residual tumor masses were removed surgically.

Results: Overall survival at one and three years was 81% (95% confidence interval [CI]: 68-94%) and 55% (CI: 38-71%), respectively. None of the patients who had positive FDG-PET findings after first line chemotherapy survived at three years after diagnosis. In contrast, 69% and 20% of patients with positive tumor markers, and 90% and 67% of patients with negative tumor markers after first line chemotherapy survived at one and three years, respectively. Negative FDG-PET after completion of treatment was also a powerful predictor of long-term survival with 100% patients surviving three years and 89% surviving five years after diagnosis.

Conclusions: Negative FDG-PET after first-line chemotherapy or after the completion of systemic treatment and resection of residual tumor masses strongly predicts long-term event-free survival in patients with EGTs.