PET/CT proved superior to conventional contrast-enhanced CT for its ability to measure treatment response and predict survival among patients with follicular lymphoma, according to results of a pooled analysis of three multicenter studies.
The findings suggest PET/CT should become a new standard for response assessment in this patient population and also could be used to help guide response-adapted therapy, researchers wrote.
Judith Trotman, MBChB, associate professor in the department of hematology at Concord Hospital at University of Sydney in Australia, and colleagues sought to examine the association between PET/CT status and survival among patients with advanced follicular lymphoma.
All 246 patients completed first-line treatment with at least six cycles of rituximab (Rituxan; Genentech, Biogen Idec) and chemotherapy. Patients underwent PET/CT and conventional CT imaging within 3 months of their last dose of induction rituximab.
Median follow-up was 54.8 months.
Forty-one (17%) patients had positive post-induction PET scan. The HR for PFS among patients with a positive PET scan compared with those who had a negative scan was 3.9 (95% CI 2.5-5.9). The HR for OS among patients with a positive PET scan compared with those who had a negative scan was 6.7 (95% CI, 2.4-18.5).
Patients with a positive PET scan were significantly less likely to achieve 4-year PFS (23.2% vs. 63.4%; P<.0001) or 4-year OS (87.2% vs. 97.1%; P<.0001).
Researchers determined the predictive power of PET status was considerably stronger than — and independent of — that of conventional CT. The 83% of patients with a negative post-induction PET scan experienced median PFS of more than 6 years, whereas the 17% of patients who had a positive post-induction PET scan had median PFS of 17 months.
Conventional CT-based response was associated with a weak predictive value of PFS (HR=1.7; 95% CI, 1.1-2.5), according to researchers.
“Our study shows that PET/CT is much better in evaluating treatment response and is an early predictor of survival,” Trotman said in a press release. “This greater accuracy will assist physicians to more effectively monitor their patients. We expect this research will result in PET/CT imaging replacing CT, becoming the new gold standard to evaluate patients with follicular lymphoma after treatment. Importantly, it will be a platform for future studies of response-adapted therapies aimed to improve the poor outcomes for those patients who remain PET positive.”
Bruce D. Cheson
The findings may lead to several clinical research opportunities, Bruce D. Cheson, MD, director of hematology research at Georgetown Lombardi Comprehensive Cancer Center, wrote in an accompanying editorial.
“One such possibility would be to assess if an early reaction to the PET scan result improves patient outcome,” Cheson wrote. “Thus, patients with a positive PET scan after induction therapy could be randomly assigned to either deferred treatment until disease progression or immediate intervention. A preferable alternative would be to introduce a unique agent at that time, such as the newly developed small molecules in a novel combination.”
Disclosure: The researchers report advisory board roles with, as well as grants and personal fees from, Celgene, Janssen, Merck, Roche, Spectrum and Takeda. The study was funded by the Lymphoma Study Association, Direction de la Recherche Clinique de l’Assistance Publique–Hopitaux de Paris, Fondazione Italiana Linfomi and the Italian Ministry of Health.