To study the influence of a family history of cancer on survival, the researchers examined Swedish cancer Registry data on 6946 patients treated for HL between 1965 and 1995.

Lymphoma refers to a malignancy of the lymph system. The disease is divided into Hodgkin's disease and Non-Hodgkin's lymphoma with the latter being much more common.

A total of 65% had undergone radiation for malignancies including nephroblastoma, neuroblastoma, non-Hodgkin's lymphoma, and tumors of the central nervous system.