18F-FDG PET or PET/CT in detecting high-grade transformation of chronic lymphocytic leukaemia and indolent lymphomas: A systematic review and meta-analysis.

Objectives: To evaluate the diagnostic accuracy of 18F-FDG PET or PET/CT in detecting histological transformation (HT) of indolent lymphomas.

Methods: A systematic search of articles up to July 2024 was performed in Embase and Medline. Eligible studies included adults with histologically proven indolent lymphoma, 18F-FDG PET or PET/CT as the index test, and sufficient data to assess diagnostic performance. Summary receiver operating characteristic curves were plotted using a bivariate model to estimate diagnostic accuracy with area under the curve (AUC).

Results: Fifteen studies with 1,307 participants were included. Ten studies assessed PET ability to detect Richter's transformation, and 5 studies focussed on HT in follicular lymphoma and other subtypes. A meta-analysis of the former showed pooled sensitivity of 0.90 (95% CI, 0.84-0.93) and specificity of 0.54 (95% CI, 0.28-0.77) when using a SUVmax threshold of around 5. AUC was 0.89. Pooled sensitivity was 0.74 (95% CI, 0.54-0.87) and specificity was 0.84 (95% CI, 0.67-0.93) when using a SUVmax threshold of around 10. AUC was 0.84. For detecting HT in follicular lymphoma, thresholds were found higher than those for Richter's transformation.

Conclusions: 18F-FDG PET or PET/CT demonstrates good diagnostic accuracy to detect Richter's transformation, best when employing SUVmax ≥ 5. SUVmax thresholds may be limited in discriminating follicular lymphoma from HT, and alternatives should be sought.

Advances in knowledge: If biopsy is feasible, SUVmax ≥ 5 can guide biopsy in patients with clinically suspicious Richter's transformation. If biopsy is infeasible, SUVmax ≥ 10 can better identify HT and guide patient management.