Cancer in siblings of children with cancer in the Nordic countries: a population-based cohort study

Familial aggregation of childhood and adult cancer in the Utah genealogy

“…1 Eleven people were counted twice because they were both a parent and a sibling of a case proband. 2 Ten people were counted twice because they were both a parent and a sibling of a control proband.…”

“…Many of these studies involved a relatively small number of cases, and Little concluded that there was no strong evidence of familial risks in parents or siblings for most of the common types of childhood cancer. Since then, several large studies of cancer risk in first-degree relatives of children with cancers of all types have emerged from the Nordic countries, 2 the United Kingdom, 3 the United States 4 and Italy. 5,6 Analyses of risk for many types of childhood cancer have also been published from the Swedish Family Cancer Database.…”

Is the risk of acute lymphoblastic leukemia reduced in siblings to children with the disease? A novel hypothesis explored by international collaboration

“…1 We here summarize these data that have led to an international collaboration, and a call for colleagues, who in their career have encountered families with two or more cases of childhood ALL in a sibship. Physicians who in their career have encountered such a family are asked to register some basic data on a one-page data sheet, which can be provided for, on request to kschmiegelow@rh.dk.…”

“…More recently, a population-and register-based study from the Nordic countries revealed only two cases of non-twin leukemia (including one undifferentiated) among approximately 11 000 non-twin siblings to 6313 children with leukemia compared to the five cases that were expected by chance. 1 As the proportion of newborns harboring preleukemic t(12;21)-positive cells probably is at least 100 times the proportion of children developing t(12;21)-positive ALL, the likelihood that such preleukemic cells degenerate further to overt ALL is 1% at the most. One explanation for the low incidence of ALL among siblings could be that, both the pre-and postnatal genetic aberrations that lead to common childhood ALL occur as random events.…”

“…8,[10][11][12][13][14][15] Why, then did the recent large population-and register-based Nordic study indicate that the risk of childhood is not increased in siblings to children with ALL and perhaps even reduced? 1 Both the presence of preleukemic cells at birth and the appropriate genetic predisposition and postnatal environment are believed to be necessary for the development of childhood ALL in the age peak group. 10 If for instance, t(12;21)-positive preleukemic cells were unlikely to occur and persist in more than one of a woman's pregnancies, the risk of ALL among the siblings to that child would be reduced to that of the remaining types of prenatally initiated cases (e.g.…”