Prognostic value of interim PET-CT in follicular lymphoma

Interim positron emission tomography-computed tomography (iPET) has shown prognostic value in high-avidity lymphomas, like diffuse large B-cell lymphoma and Hodgkin lymphoma. However, its role in follicular lymphoma (FL) remains unclear.

We conducted a retrospective observational study including patients with grades 1-3a FL treated with frontline chemoimmunotherapy between 2012 and 2014 at our institution, who underwent iPET after the fourth treatment cycle. All PET-CT were re-evaluated to assign Deauville 5-point scale (D5PS) and we considered complete metabolic response (CMR) when D5PS was 1-3. Primary endpoints were progression-free survival (PFS) and overall survival (OS).

Of the 38 patients included, 63.2% (24/38) achieved CMR on iPET. All the patients who were in CMR on iPET, were also in CMR at the end of treatment PET-CT. However, among the 14 patients without CMR on iPET, only 4 patients achieved CMR at end of treatment PET-CT and 5 patients had progressive disease. After a median follow-up of 87.6 months (range 11.0-129.8), achieving CMR was associated with longer PFS (p<0.001; HR 0.08; 95% CI 0.03-0.24) and longer OS (p=0.012; HR 0.24; 95% CI 0.07-0.80).

In this single-center study with long follow-up, iPET evaluated by D5PS predicted PFS and OS in FL.