A study just published in the prestigious British Journal of Cancer by researchers at the University of Otago's Christchurch School of Medicine and Health Sciences and Dunedin School of Medicine, and the University of Melbourne, has found evidence of a link between a common virus and breast cancer in women under the age of 40 years.
The research suggests that those women who are exposed in adulthood to the virus, cytomegalovirus, may have a greater risk of developing breast cancer, the most common cancer affecting women in New Zealand. 377 women were included in the study, and blood samples were taken to measure antibody levels to cytomegalovirus, and to another virus; Epstein-Barr virus.
"Countries where most people are exposed to cytomegalovirus and other viruses in childhood, have lower rates of breast cancer," says principal researcher Dr Ann Richardson.
"Our study found that women with breast cancer had higher cytomegalovirus antibody levels than women without breast cancer. The higher antibody levels could be the result of more recent infection with cytomegalovirus. This may mean that late infection with cytomegalovirus,rather than in childhood, is a risk factor for breast cancer".
Dr Richardson says that it is not unusual to find links between viruses and increased cancer risk. Several cancers such as cervical, liver, and some forms of leukaemia are known to be caused by viruses. Breast cancer in mice can also be caused by a virus. Cytomegalovirus or CMV is a common virus that is shed in breast milk as well as saliva, urine, cervical secretions and semen.
The study also investigated links between another virus, Epstein-Barr, and breast cancer but the results are negative.
At present it is still scientifically unclear exactly how CMV might cause or influence the development of breast cancer. Dr Richardson says that further research is needed. The most exciting possibility is, if late infection with CMV does increase the risk of breast cancer, it could be possible to decrease the risk by exposing people to the virus by immunisation in childhood.
Around 2000 women develop breast cancer every year in New Zealand, but most are over the age of 40. Further research is needed to investigate this possible link between cytomegalovirus and breast cancer. This study was supported by the Cancer Society of New Zealand, which funded the antibody testing of the blood samples.