Retrospective Cohort Study Assessing the Prognostic Value of Baseline Necrosis on PET-CT in Hodgkin Lymphoma

Background: Identifying prognostic markers at diagnosis is essential to determine optimal tailored therapy for patients. The presence of necrosis has been shown to be associated with worse outcomes in patients with diffuse large B cell lymphoma. We aimed to determine whether necrosis at baseline correlated with clinical outcomes in patients with Hodgkin lymphoma.

Methods: Baseline PET-CT scans of patients diagnosed with Hodgkin lymphoma between January 2015 and December 2016 at a large UK teaching hospital were reviewed for evidence of tumour necrosis by a consultant radionuclide radiologist with a specialist interest in lymphoma. Potential necrosis identified on PET-CT was then confirmed both visually and quantitatively on baseline contrast enhanced CT. The presence or absence of necrosis was correlated with prognostic markers including Total Metabolic Volume (TMV), Total Lesion Glycolysis (TLG) and Hasenclever score as well as metabolic response, current remission status, relapse outcome and mortality.

Results: Fifty one patients' PET-CT scans were reviewed in total. Eight (15.6%) patients were confirmed to demonstrate necrosis both visually and using quantitative criteria. The presence of necrosis was associated with increased mortality (38%) vs no necrosis (9%). At end of treatment, a lower rate of complete metabolic response was achieved in the necrosis cohort (37%) compared with the no necrosis cohort (74%). This was statistically significant using Chi-square test with Yates correction (p=0.049). The presence of necrosis did not correlate with other prognostic markers (TMV, TLG or Hasenclever score).

Conclusion: This study has found that baseline necrosis correlated with both mortality and incomplete metabolic response following initial treatment. Tumour necrosis did not correlate with other prognostic markers and therefore may be able to be used as an independent assessment of prognosis to allow further tailoring of patient treatment. This study has identified a new potential independent prognostic marker in Hodgkin lymphoma. Prospective trials are required to confirm or refute these findings.