Abstract

In a population-based case-control study in Sweden on multiple myeloma, the occurrence of different diseases in relatives, particularly hematologic malignancies and different types of cancer, was investigated. Through a questionnaire mailed to all living subjects, i.e. cases and controls, and to the next-of-kin for deceased subjects, information was obtained on malignant and certain other diseases among relatives. All malignant diseases reported among first-degree relatives were verified, if possible, through parochial authorities and the Swedish Cancer Register. In total, data from 239 cases with myeloma and 220 controls were analyzed. An increased risk was found for persons with first-degree relatives with hematologic malignancies (relative risk [RR] = 2.36, 90 percent confidence interval [CI ) = 0.90-6.15), and also with multiple myeloma specifically (RR = 5.64, CI = 1.16-27.51). An increased risk also was seen if the close relatives had experienced another tumor disease (RR = 1.21, CI = 0.86-1.71). Particularly, occurrence of prostatic cancer (RR = 3.11, CI = 1.25-7.71) or brain tumor (RR = 6.61, CI = 1.42-30.67) in relatives increased the risk for multiple myeloma.