PET-CT as Standard for Response Assessment After First-Line Therapy in Follicular Lymphoma
In a pooled analysis reported in The Lancet Haematology, Trotman et al found that 18F-fluorodeoxyglucose (FDG) positron-emission tomography/low-dose computed tomography (PET-CT) provides improved prognostic information over conventional contrast-enhanced CT in assessment of response to first-line therapy in follicular lymphoma.
Study Analysis
The analysis involved data from three multicenter prospective studies of first-line rituximab (Rituxan) chemotherapy for patients with high-tumor-burden follicular lymphoma (PRIMA, PET-Folliculaire, and Fondazione Italiana Linfomi FOLL05 studies). Patients included in the analysis received at least six cycles of rituximab and chemotherapy before response assessment with conventional contrast-enhanced CT and PET-CT. Only patients with a PET-CT scan within 3 months of the last dose of induction rituximab were included. Scans undergoing central PET-CT review were scored independently by three reviewers according to the 5-point Deauville scale, with positive scans having a score of ≥ 4.
Between December 2004 and September 2010, 439 of the patients in the three studies underwent local PET-CT assessment, with 246 having centrally reviewed postinduction scans. Of these, 17% had positive results.
Survival According to PET-CT
After median follow-up of 54.8 months, median progression-free survival was 74 months vs 16.9 months in patients with negative vs positive PET-CT scans (hazard ratio [HR] = 3.9, P < .0001) and median overall survival was not reached vs 78.7 months (HR = 6.7, P = .0002). Four-year progression-free survival was 63.4% vs 23.2% (P < .0001) and 4-year overall survival was 87.2% vs 63.4% (P < .0001).
Among patients with complete, unconfirmed complete, or partial response on conventional CT, median progression-free survival was 89.5% in those with negative PET-CT vs 19.6% in those with positive PET-CT (P < .0001) and median overall survival was not reached vs 78.7 months (P < .0001). Conventional CT-based response (complete or unconfirmed complete response vs partial response) was weakly predictive of progression-free survival (HR = 1.7, P = .017). Complete response vs unconfirmed complete response vs partial response on conventional CT was not predictive of overall survival.
The investigators concluded: “PET-CT rather than contrast-enhanced CT scanning should be considered as a new standard for response assessment of follicular lymphoma in clinical practice, and could help guide response-adapted therapy.”
Judith Trotman, MBChB, of University of Sydney, is the corresponding author for the Lancet Haematology article.
The study was funded by Groupe d'Etude des Lymphomes de l'Adulte (Lymphoma Study Association), Direction de la Recherche Clinique de l'Assistance Publique-Hôpitaux de Paris, Fondazione Italiana Linfomi, and Italian Ministry of Health. For full disclosures of the study authors, visit www.thelancet.com.
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