Evaluation of the prognostic role of tumour-associated macrophages in newly diagnosed classical Hodgkin lymphoma and correlation with early FDG-PET assessment

In Hodgkin Lymphoma (HL), about 20% of patients still have relapsed/refractory disease and late toxic effects rate continue to rise with time. ‘Early FDG-PET’ and tissue macrophage infiltration (TAM) emerged as powerful prognostic predictors. The primary endpoint was to investigate the prognostic role of both early FDG-PET and TAM; the secondary endpoint was to test if early FDG-PET positivity could correlate with high TAM score.A cohort of 200 HL patients was analysed. Induction treatment plan consisted of two to six courses of ABVD and, if indicated, involved field radiation therapy. All patients repeated CT scan and FDG-PET after two cycles and after the completion of therapy. TAM in diagnostic specimens was determined by immunohistochemistry with a monoclonal antibody (anti-CD68 KP1). Overall, early FDG-PET was negative in 163 patients (81.5%) and positive in 37 patients (18.5%), showing a significant correlation with the achievement of CR (p<0.0001). After a median follow-up of 40months, progression free survival (PFS) was significantly better for PET negative patients (p<0.0001). CD68 expression was low, intermediate or high in 26 (13%), 100 (50%) and 74 (37%) cases, without difference in the distribution between responders and non-responders. PFS analysis showed no significant difference in any score group. TAM score did not show any correlation with early FDG-PET result.This study confirms that early FDG-PET has a high prognostic power, while TAM score does not seem to influence the outcome; in contrast to our original hypothesis, it does not correlate with FDG-PET assessment.