Establishment and validation of a clinical threshold criteria for choosing PET imaging tracers for indolent non-Hodgkin's lymphoma.

[BACKGROUND] [F]FDG PET-CT scan has a lower sensitivity in imaging of indolent non-Hodgkin's Lymphoma (NHL.) We aimed at identifying a threshold of clinical/pathological indicators which would independently predict [F]FDG PET-CT scan positivity. For this purpose, we used a retrospective real-world cohort of NHL patients and then validated this criterion on [F]FDG and [Ga]Pentixafor scans in a prospective indolent NHL cohort.

[RESULTS] In the retrospective real-world cohort of NHL, Ki67 was identified as an independent factor that influenced [F]FDG uptake (r = 0.701). The cutoff value for Ki67 was 36.5% with a maximum area under the curve (AUC) of 0.811 and a Youden index of 0.494 for predicting [F]FDG imaging positivity. The sensitivity of [F]FDG PET in retrospective NHL cohort was only 65.2% (101/155) which further decreased to 46.3% in patients with Ki 67 ≤ 35%. In the prospective comparison of patients with Ki67 ≤ 35%, [Ga]Pentixafor had a higher sensitivity (80.6% (29/36)) than that of [F]FDG PET-CT scan (30.6% (11/36)). However, in patients with Ki67 > 35%, both the imaging modalities had similar sensitivities of 60% (3/5).

[CONCLUSION] A Ki67 of 35% was shown to be a promising threshold criterion for choosing between [F]FDG or [Ga]Pentixafor PET tracer in patients with indolent NHL.

[TRIAL REGISTRATION] A Study Evaluating the Value of 68Ga-Pentixafor PET Imaging in the Staging of Hematological Tumor, and Comparing it With 18 F-FDG PET/CT Imaging, NCT06834412. Registered 13 February 2025 - Retrospectively registered, https://register.

[CLINICALTRIALS] gov/prs/beta/studies/S000FBBP00000062 .