Case Pairs With Chronic Granulocytic Leukemia Age, y Sex (Diagnosis Dates) Opportunity for Contact Region Observers East Anglia, F/F 27 (1969)/32 (1974) Next-door neighbor United Kingdom H.G.H.R. M/M 46(1981)/50(1983) Worked in same office Albany, NY A.S.D.S. Saint Albans, F/F 44 (1981)/37 (1982) Taught in same school United Kingdom D.A.G.G. Swindon, M/M 20(1981)/35(1984) Worked in same office United Kingdom H.C.D.
To the Editor.—
Despite the many reports of clusters of cases of leukemia, results of formal studies have on the whole been disappointing.1 Most of the studies have, however, concerned acute leukemia. Four instances have come to our notice in which two individuals with appreciable personal contact have developed chronic granulocytic leukemia (Table).The annual age-adjusted world population incidence of chronic granulocytic leukemia recorded in most US and British cancer registries is approximately ten per million, so examples of such pairs of cases cannot often occur by chance. We recognize that