Post-Induction PET-CT ‘Gold Standard’ for Follicular Lymphoma

PET-CT after induction therapy for follicular lymphoma predict progression-free and overall survival

medwireNews: Positron emission tomography/computed tomography (PET–CT) scanning/imaging should be used for measuring first-line treatment response in patients with Follicular lymphoma, suggests research published in The Lancet Haematology.

Pooled analysis of data from three multicentre studies shows that PET–CT imaging was significantly better at predicting progression-free survival (PFS) after rituximab plus chemotherapy than conventional contrast-enhanced CT imaging, report lead author Judith Trotman, from the University of Sydney in New South Wales, Australia, and colleagues.

“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”, Judith Trotman commented in a press release.

“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.”

The study included data for 246 participants of the PRIMA, PET-Folliculaire and FOLL05 studies who were assessed by both PET and conventional CT within 3 months of their last induction rituximab dose and had their post-induction scans independently reviewed by three reviewers.

Overall, 17% of patients had a positive PET scan, defined as at least 4 points on the 5-point Deauville criteria for 18F-fluorodeoxyglucose (FDG) uptake in lymphoma patients. This indicated that lesion uptake of FDG was moderately higher than uptake in the liver (4 points) or that FDG uptake in lesions was markedly higher than that in the liver and/or that uptake showed the presence of new lesions (5 points).

Four-year PFS and overall survival were achieved by significantly fewer patients with a positive PET scan than those with a negative scan, with rates of 23.3% versus 63.4% and 87.2% versus 97.1%, respectively.

This gave a significant hazard ratio (HR) for PFS of 3.9 for patients with a positive versus negative scan, with a corresponding significant HR of 6.7 for overall survival.

By comparison, a complete or unconfirmed complete response on a conventional CT scan was only “weakly predictive” of PFS, at a HR of 1.7 versus a partial response, the researchers report.

And further analysis showed that a positive PET scan was more predictive of survival than the Follicular Lymphoma International Prognostic Index (FLIPI), FLIPI2, and a marrow-based response assessment using the 1999 International Workshop Criteria.

“Although these results are reassuring for patients who have a negative PET 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”, Judith Trotman and co-authors recommend.

Bruce Cheson, from Georgetown University Hospital in Washington DC, USA, suggests in an accompanying comment that the findings open up research opportunities for follicular lymphoma, such as determining whether post-induction PET scan results should be used to direct patients to immediate or deferred interventions.

He writes that the “most crucial need” is to identify biomarkers that can distinguish between patients with positive and negative post-induction scans and exploit this information to improve induction regimens.

“In the meantime, the data from Trotman and colleagues provide valuable support that PET-CT provides a readily available surrogate endpoint with which to more rapidly develop better therapies for a population of patients with a predictably poor outcome”, the commentator concludes.

References

Trotman J, Luminari S, Boussetta S, et al. Prognostic value of PET-CT after first-line therapy in patients with follicular lymphoma: a pooled analysis of central scan review in three multicentre studies. Lancet Haematol 2014; Early online publication 18 September. doi:10.1016/S2352-3026(14)70008-0

Cheson B. PET-CT restaging: a surrogate for follicular lymphoma. Lancet Haematol 2014; Early online publication 18 September. doi:10.1016/S2352-3026(14)70015-8

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