Dr Dong Pang told the gathering of international cancer experts that among the mothers of 2,604 children who were diagnosed with a solid tumour when they were younger than 15, there were 95 cases of breast cancer a third higher than the expected number of 73.5.
The risk of breast cancer increased if the child was diagnosed with cancer at a younger age than the median age of the study (5.7 years) or if the affected child was a boy. There were 51 cases of breast cancer amongst mothers of younger children, while only 34 were expected (an increased risk of one half), and 64 cases of breast cancer amongst the mothers of boys, while only 40.4 were expected (an increased risk of three fifths).
Dr Pang, an epidemiologist with the Cancer Research UK Paediatric and Familial Cancer Research Group at the Royal Manchester Children's Hospital, UK, told the conference that the increased risk of breast cancer among mothers of children with solid tumours might be due to some form of mother-foetal interaction during pregnancy, and that hormones might play a role.
"Our study shows that mothers of children with certain types of tumours are at increased risk of developing breast cancer. The risk is higher in mothers of children who are younger than usual at the time of diagnosis of their tumours, and in mothers of boys with tumours. Also the risk of breast cancer is higher during the early years following the birth of the child who subsequently develops cancer," said Dr Pang.
"We know that germline mutations in certain genes, particularly the tumour suppressor gene, p53*, greatly increase the risk of both breast cancer in young women and certain tumours in children for example embryonal rhabdomyosarcoma, a tumour of the muscle that is
Contact: Emma Mason
Federation of European Cancer Societies