Identification of factors associated with high breast cancer risk in the mothers of children with soft tissue sarcoma.

Information on the past medical history of the mothers of a population-based series of 177 children with soft tissue sarcoma was obtained by interview and from medical records. Eight mothers developed breast cancer, six premenopausally, compared with 3.26 expected (P = .04), but no excess of other types of cancers was detected. High breast cancer risk was associated with the following factors in the index child: age at diagnosis less than 24 months (relative risk [RR], 7.84), embryonal rhabdomyosarcoma (RR, 3.74), and male sex (RR, 3.02). Characteristics in the mother associated with high breast cancer risk were the following: late age at first birth (RR, 5.13), late age at birth of index child (RR, 5.69), and high birth-rank order of index child (RR, 4.08). The results suggest there may be a subset of childhood soft tissue sarcoma with a predominantly genetic etiology. The association between premenopausal breast cancer in the mother, late age at birth of index child, and early onset of soft tissue sarcoma in the index child suggests that these three events are not independent and that interactions between genetic and other factors may be important. The identification of a group of women at high risk for breast cancer affords an opportunity for screening and early detection. The study of cancer family syndromes may provide insights into underlying mechanisms in cancer genetics.