F-18 positron emission tomography combined with low-dose computed tomography was more effective than conventional CT or the Follicular Lymphoma International Prognostic Index for predicting treatment response in patients with advanced follicular lymphoma, authors of a pooled analysis reported online in the Lancet Haemotology.
“Although these results are reassuring for patients who have a negative PET [positron emission tomography] scan, those who have a positive PET scan after first-line therapy can no longer be regarded as having an indolent disease and should be closely monitored,” wrote Dr. Judith Trotman at the University of Sydney, Australia, and her associates.
Follicular lymphoma often recurs after treatment, but predicting early relapsers has been a challenge, the investigators noted. They performed a masked review of three prospective, multicenter studies of 246 patients with follicular lymphoma, finding that patients with negative postinduction PET-CT scans (scores of less than four on the five-point Deauville scale) had median progression-free survival (PFS) of more than 6 years, compared with a median PFS of only 16.9 months for PET-positive patients (P = .0001). The markedly shorter PFS occurred even though most patients received anthracycline (CHOP/FM), the researchers said (Lancet Haematol. 2014 Sept. 18 [doi:10.1016/ S2352-3026(14)70008-0]).
Four years after induction, 63.4% of PET-negative patients were progression free, compared with only 23.2% of PET-positive patients (P less than .0001), the investigators added. And 4-year overall survival in PET-negative patients also was significantly higher than in PET-negative patients (97.1% vs. 87.2%; P less than .0001), they reported.PET status also was “much stronger” than the Follicular Lymphoma International Prognostic Index, FLIPI2, or contrast-enhanced CT for predicting outcomes in conventional responders, Dr. Trotman and her associates said. Conventional CT response only weakly predicted progression-free survival (P = .017), while a FLIPI2 score of 3-5 predicted progression-free survival (P = .011) but not overall survival. For this reason, responders historically have faced “an uncertain remission” and need close clinical follow-up, they pointed out.
The study was funded by the Lymphoma Study Association, Direction de la Recherche Clinique de l’Assistance Publique–Hôpitaux de Paris, Fondazione Italiana Linfomi, and the Italian Ministry of Health. Dr. Trotman reported uncompensated advisory relationships with Roche and Janssen, and three of 18 coauthors reported financial relationships with Merck, Celgene, Roche, Takeda, Janssen, and Spectrum. The rest reported having no conflicts of interest.