Interim fluorine-18 fluorodeoxyglucose positron emission tomography for early metabolic assessment of therapeutic response to chemotherapy for metastatic transitional cell carcinoma.

Background: The prognostic impact of early metabolic response by fluorine-18 fluorodeoxyglucose positron emission tomography (FDG-PET) after 2 cycles of first-line chemotherapy is still unrecognized in metastatic transitional cell carcinoma (TCC). Patients and Methods: Patients with metastatic TCC receiving the modified combination of methotrexate, vinblastine, doxorubicin, and cisplatin (MVAC), according to institutional protocol, underwent computed tomography (CT) and FDG-PET imaging at baseline, a restaging with PET imaging after 2 cycles only (PET2), and a CT (+/- FDG-PET) scan at the end of treatment and during follow-up. Progression-free survival (PFS) and overall survival (OS) were estimated with the Kaplan-Meier method; univariate (UVA) and multivariate (MVA) Cox models were fitted. Prespecified variables were the presence of visceral metastases, nodal or soft tissue disease, and early PET response. Results: In the period from May 2010 to October 2012, 31 patients with Eastern Cooperative Oncology Group performance status 0 received the modified MVAC regimen every 3 weeks. In all, 6 patients (19.3%) had a complete response (CR) and 17 (54.8%) a partial metabolic response (PR), 4 had stable disease (SD), and 4 progressed. PET2 responders had a median PFS of 8 months (95 % CI, 7-11 mo) compared with 3 months (95 % CI, 2-5 mo) of patients without response (P = .024). They also had a significant benefit in 8-month PFS (P < .001 via Klein test) and 15-month OS (P = .016). PET2 response was significant for PFS in both UVA and MVA Cox models (P = .027 and P = .023, respectively). Conclusion: PET response after 2 cycles of first-line chemotherapy, compared with detection by early CT, was associated with longer PFS and OS in advanced TCC and warrants further investigation in the field.