Risk of multiple primary malignancies following treatment of Hodgkin lymphoma.

We assessed risk, localization, and timing of third malignancies in Hodgkin lymphoma (HL) survivors. In a cohort of 3122 5-year HL survivors diagnosed before the age of 51 years and treated between 1965 and 1995, we examined whether risk factors for second and third malignancies differ and whether the occurrence of a second malignancy affects the risk of subsequent malignancies, using recurrent event analyses. After a median follow-up of 22.6 years, 832 patients developed a second malignancy and 126 patients a third one. The risk of a second malignancy was 4.7-fold increased (95% confidence interval [CI], 4.4-5.1) compared with risk in the general population; the risk for a third malignancy after a second malignancy was 5.4-fold (95% CI, 4.4-6.5) increased. The 10-year cumulative incidence of any third malignancy was 13.3%. Compared with patients still free of a second malignancy, patients with a second malignancy had a higher risk of developing subsequent malignancies. This risk depended on age, with hazard ratios of 2.2, 1.6, and 1.1 for patients aged <25, 25 to 34, and 35 to 50 years at HL treatment, respectively. In HL survivors who had a second malignancy, treating physicians should be aware of the increased risk of subsequent malignancies.