Does interim fluorodeoxyglucose-PET have predictive value?

Hugo Adams and Thomas Kwee, based in the Netherlands, recently wrote a correspondence in the Journal of Clinical Oncology, Oct 2016, in response to an article by Press et al. who presented the results of a US intergroup study that used interim FDG-PET imaging to decide whether or not to keep stage III-IV HL patients on ABVD or switch them to eBEACOPP.

Highlights:

• 358 patients enrolled, 336 evaluable
• PET scan after two ABVD cycles
• Deauville score 1–3 = pts received 4 more cycles ABVD
• Deauville score 4–5 = pts switched to 6 cycles eBEACOPP
• 82% pts were PET-negative so stayed on ABVD, 18% were PET-positive and were switched to eBEACOPP
• 2-year PFS estimate: PET-neg = 82%, PET-pos = 64%

One of the main issues with the study that Adams & Kwee present is that no control arm was used to compare against standard ABVD treatment. Furthermore, Adams & Kwee detailed a meta-analysis that did not support Press et al.’s claim that positive interim FDG-PET is associated with very poor prognosis. Additionally, Adams & Kwee state that follow-up FDG-PET has a high false-positive rate, but the authors did not report the histopathological confirmation of disease, and current PET techniques have poor resolution resulting in the possibility that small lymphocytic deposits may be missed. Adam & Kwee also state that using a more intense treatment option is only justified in cases where there is a proven significant difference in PFS and OS, which was not demonstrated in the paper. In conclusion, Adams & Kwee state that in patients with advanced HL, interim FDG-PET may not be as useful in improving outcomes as Press et al.suggest, and more work is needed to confirm any potential.