Comparison of 18F-labelled fluoro-2-deoxyglucose-PET with conventional computed tomography for staging and response assessment in paediatric and adult patients with nodular lymphocyte-predominant Hodgkin's lymphoma.

Background: Nodular lymphocyte-predominant Hodgkin lymphoma (NLPHL) is an uncommon subtype of Hodgkin lymphoma. Data are limited regarding 18F-labelled fluoro-2-deoxyglucose (FDG)-PET use in NLPHL. We are reporting our experience with FDG-PET utility in staging and response assessment NLPHL patients.

Methods: We retrospectively studied a population of all newly diagnosed or relapsed/refractory patients who underwent both pre-treatment contrast-enhanced computed tomography (CeCT) and an FDG-PET and also at the end of planned treatment.

Results: We identified 68 patients found to have in total 312 scans, 78 paired pre-therapeutic and post-treatment CeCT and FDG-PET scans. Among them, 55 were male, with a median follow-up was 48 months. Median SUV-max was 8.3 (2.0-21.0). FDG-PET and CeCT were concordant in 80% (62/78) of staging scans. In 20% (16/78) of patients in whom a discordance was observed, FDG-PET resulted in upstaging in 13 scans and downstaging in 3 scans. The sensitivity of CeCT was 92% for nodal staging and 42% for extralymphatic staging when compared to FDG-PET. The specificity of CeCT was 98% as compared to FDG-PET. For response assessment, there was poor agreement between the CeCT and FDG-PET in assigning complete remission of disease scores as FDG-PET was able to identify the absence of disease despite the presence of a radiologically evident residual mass on CeCT. The sensitivity for CeCT compared to FDG-PET was 100% while the specificity was 43% for detection of post-treatment response.

Conclusion: For NLPHL, pre-therapeutic FDG-PET scan is better than CeCT staging. FDG-PET has much better specificity for response assessment than CeCT.