Interim ¹⁸F-Fluorodeoxyglucose Positron Emission Tomography for Early Metabolic Assessment of Response to Cisplatin, Etoposide, and Bleomycin Chemotherapy for Metastatic Seminoma: Clinical Value and Future Directions

Background: In patients with metastatic seminoma, designing a risk-adapted strategy that may help personalize the burden of treatment and follow-up is required. Patients and Methods: Patients who were administered cisplatin, etoposide, and bleomycin (PEB) were staged at baseline with computed tomography (CT), positron emission tomography (PET), and serum tumor markers. Restaging was then performed with PET after 2 cycles of PEB (PET₂) and with CT after 3 to 4 cycles of treatment. The 20% cutoff of maximal standardized uptake value (SUV_max) changes and Response Evaluation Criteria in Solid Tumors (RECIST, version 1.1) criteria were applied to define the response. The Wilcoxon rank sum test was used to analyze the association between metabolic response and the shrinkage of target lesions. Results: Between February 2009 and November 2013, 37 patients were enrolled. After 2 cycles of PEB, 27 patients (72.9%; 95% confidence interval [CI], 55.8-86.2) had a metabolic complete response (CR) and 10 patients had a partial response (PR; 27%; 95% CI, 13.8-44.1). A significant association was found between PET₂ response and baseline (P = .003), final diameter (P <.001), and percentage of tumor shrinkage (P = .014) of target lesions. After 18 months' (interquartile range [IQR], 13-23) median follow-up, 2 patients with PET₂ PR had relapsed disease; none of those with a CR had relapsed disease. Conclusions: A significant association was found between early metabolic response and tumor shrinkage in patients with advanced seminoma. Patients achieving a PET₂ CR could be predicted not to need additional treatment after PEB, and simplifying their follow-up should be an end point. PET₂ might also identify difficult to treat cases at an early stage.