The frequency of change in five-point scale score with a Bayesian penalised likelihood PET reconstruction algorithm on interim FDG PET-CT and its potential implications for therapy decisions in Hodgkin's lymphoma

AIM: To assess the effect of a Bayesian penalised likelihood (BPL) reconstruction algorithm on the five-point scale (5-PS) score, response categorisation, and potential implications for therapy decisions after interim 2-[18F]-fluoro-2-deoxy-D-glucose (FDG) positron-emission to-mography (PET)-computed tomography (CT) (iPET-CT) to guide treatment in classical Hodg-kin's lymphoma (HL). MATERIALS AND METHODS: The present study included new patients with HL undergoing iPET-CT from 2014-2019 after two cycles of doxorubicin (Adriamycin), bleomycin, vincristine, and dacarbazine (ABVD). Two reporters categorised response using the 5-PS and measured maximum standardised uptake values (SUVmax) of the most avid tumour residuum, medias-tinal blood pool, and normal liver with ordered subset expected maximisation (OSEM) and BPL reconstructions.RESULTS: Eighty-one iPET-CT examinations were reviewed. Compared with OSEM, BPL increased the 5-PS score by a single score in 18/81 (22.2%) patients. The frequency of potential treatment intensification by changing a score of 3-4 was 13.6% (11/81) and represented 25% (11/44) of patients with a score of 3 on OSEM. All 11 patients remained in remission without a change in therapy (mean 63 months) except one who required second-line treatment for re-fractory disease. Median SUVmax of tumour residuum was significantly higher with BPL compared with OSEM (2.7 versus 2.4, p<<0.0001), whilst liver SUVmax was significantly lower for both reporters (up to 6.6%, p<0.0001).CONCLUSION: BPL PET reconstruction increased the 5-PS score on iPET-CT in 22% of HL patients and can potentially result in unnecessary treatment escalation in over half of these patients.(c) 2022 The Author(s). Published by Elsevier Ltd on behalf of The Royal College of Radiologists. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/ 4.0/).