Baseline SUVmax did not predict histological transformation in the phase 3 GALLIUM study in follicular lymphoma

A minority of patients with follicular lymphoma (FL) undergo histological transformation (HT). This retrospective analysis of 549 patients from the phase 3 GALLIUM study (NCT01332968) assessed the relationship between baseline maximum standardized uptake value (bSUVmax) on positron emission tomography (PET) and HT risk. Previously untreated patients with high tumor burden grade 1-3a FL received obinutuzumab- or rituximab-based chemotherapy induction. The relationship between bSUVmax and HT risk was assessed using cutoff values for SUVmax of >10 and >20. Overall, 15/549 (2.7%) patients with baseline PET scans experienced biopsy-confirmed HT (median follow-up: 59 months). Over 65% of patients had a bSUVmax >10, with 3.3% of these experiencing HT. Only 1/74 (1.4%) patients with a bSUVmax >20 underwent HT. Median bSUVmax in patients with versus without HT was 12.4 (range, 8.1-28.0) versus 11.8 (range, 3.1-64.4), respectively; median bSUVrange (the difference between bSUVmax of the most and least 18F-fluorodeoxyglucose-avid lymphoma sites) was 8.0 (range, 1.1-23.9) versus 7.1 (range, 0.0-59.8), respectively. There was no temporal relationship between bSUVmax and HT. Neither bSUVmax nor bSUVrange predicted HT in GALLIUM, suggesting there may be little benefit in re-biopsy of lesions to exclude HT based on SUVmax alone before initiating therapy in patients with high tumor burden FL.