Prognostic Role of Early Interim Fluorodeoxyglucose Positron Emission Tomography in Patients With Advanced Seminoma Undergoing Standard Treatment.

Background: Patients with advanced seminoma have an exceedingly favorable prognosis. Studies aiming to reduce the total treatment burden and side effects in patients with well-defined disease and very good prognosis are warranted.
Patients and Methods: In a prospective observational study, patients with advanced stage seminoma were treated with bleomycin, etoposide, and cisplatin (BEP) or EP according to guidelines. Fluorodeoxyglucose with positron emission tomography and computed tomography (FDG-PET/CT) examinations were performed at baseline, after 2 cycles (PET/CT2) in all patients, and after chemotherapy at the physician's discretion. Disease response to treatment assessed by PET/CT was qualitatively evaluated by 2 independent nuclear medicine physicians. Contrast-enhanced CT scans were also performed according to guidelines (at baseline, after treatment, during follow-up). The study's primary endpoint was to evaluate the association between PET/CT2 findings and relapse-free survival.
Results: From January 2009 to January 2017, a total of 75 consecutive patients were enrolled, of whom 70 were included for analysis. The clinical disease stage was IIA-B and IIC-III in 40% and 60%, respectively. By local assessment, 46 PET/CT2 scans (65.7%) were reported as negative, and 46% of these patients had stage IIC-III disease. Five-year relapse-free survival of PET/CT2-positive patients was 75% (95% confidence interval, 60-95) compared to 97.8% (95% confidence interval, 93.7-100) of PET/CT2-negative patients (P = .002). In univariate analyses, PET/CT2 was significantly associated with relapse-free survival (P = .02).
Conclusions: No residual FDG uptake after 2 cycles of conventional chemotherapy is prognostic in advanced seminoma, but it may be useful to optimize the standard prognostic risk groups and may be tested within larger prospective clinical trials of chemotherapy deescalation.
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