The incidence of lymphoma in first-degree relatives of patients with Hodgkin disease and non-hodgkin lymphoma - Results and limitations of a registry-linked study

BACKGROUND. The precise incidence of familial Hodgkin disease (HD) and non- Hodgkin lymphoma (NHL) in first-degree relatives is unknown. Through record linkage using two population-based sources, the authors estimated the risk of HD and NHL in family members of lymphoma probands. METHODS. The authors identified 8037 first-degree relatives of 2606 lymphom a the Israel Cancer Registry, then calculated the standardized incidence ra tio (SIR) by dividing the observed number of cases with the expected, adjus ting for age, gender, calendar year, and continent of origin. RESULTS. The family file yielded incomplete ascertainment of relatives (for 771 probands, no relatives were identified). Twenty cases of lymphoma-6 HD and 14 NHL-were identified among relatives of lymphoma patients. The SIR f or HD was 1.15 (95% confidence interval [CI]: 0.42-2.51) and for NHL 1.71 ( 95% CI: 0.93-2.87), considering the entire population of first-degree relat ives. SIRs among siblings of lymphoma probands were 3.12 (95% CI: 1.01-7.29 ) for HD, 2.16 (95% CI: 0.45-6.31) for NHL, and 2.68 (95% CI: 1.15-5.27) fo r all lymphomas. There were 4 HD/HD, 1 NHL/NHL, and 3 NHL/HD sibling pairs. For HD/HD and NHL/NHL sibling pairs, the interval between lymphoma occurre nce in proband and sibling was 1-4 years, whereas for HD/NHL pairs this ran ged from 16 to 21 years. CONCLUSIONS. The risk of lymphoma among siblings of lymphoma probands was o ver 2.5-fold that of the general population and lower among other family me mbers. The temporal proximity of HD/HD and NHL/NHL sibling pairs argues for environmental as well as genetic etiology. This method was hampered by inc omplete data. Cancer 2000;88:2357-66. (C) 2000 American Cancer Society.