Late recurrence of lymphoid malignancies after initial treatment for Hodgkin lymphoma - A study from the Danish Lymphoma Registry.

We analysed a large cohort of Hodgkin lymphoma (HL) patients in order to characterize: (1) the pattern of late recurrence of lymphoid malignancies (LR) after initial treatment for HL over a 35-year period; (2) the clinicopathological parameters influencing the risk of LR; and (3) the outcome of patients experiencing LR. We reviewed data of 3350 HL patients diagnosed in Denmark between 1982 and 2018 and registered in the Danish National Lymphoma Registry (LYFO). LR was defined as a recurrence of lymphoid malignancy at least five years after initial diagnosis. LR occurred in 58 patients, with a cumulative incidence at 10, 15 and 20 years of 2.7%, 4.0% and 5.4% respectively. LR was more frequently observed in patients with nodular lymphocyte-predominant HL (NLPHL) [hazard ratio (HR) 4.5; 95% confidence interval (CI): 2.4-8.4, p < 0.001]. In classical HL (cHL) patients, older age and lymphocytopenia were risk factors for LR with HRs of 1.04 per additional year (95% CI: 1.02-1.06) and 5.6 (95% CI: 2.7-11.5) respectively. Mixed cellularity histological subtype was a risk factor for LR, but only in females, with a HR of 5.4 (95% CI: 1.4-20.4, p = 0.014). In contrast to what was observed in NLPHL, LR in cHL was associated with an almost threefold increased risk of death compared with patients in continuous complete remission. Approximately one fifth (22.4%) of patients with LR experienced a second relapse.