Friday 10 May 2013
Women undergoing radiotherapy for Hodgkin lymphoma have an increased risk of developing breast cancer the closer their treatment is to their first menstrual period, a new study reports.
But scientists from The Institute of Cancer Research, London, with collaborators from hospitals around England and Wales, found that pregnancy did not convey any extra risk to Hodgkin lymphoma patients.
Researchers found that patients with Hodgkin lymphoma given a treatment called supradiaphragmatic radiotherapy (sRT) faced more than a three-fold increase in the risk of developing breast cancer in later life if the treatments were within two years of their period starting.
Previous research conducted at The Institute of Cancer Research (ICR) has found young women treated with sRT for Hodgkin lymphoma have an almost one in two chance of developing breast cancer in a 40-year period after their treatment.
But there has been little research into how the onset of a woman’s menstrual cycle, as their breasts are developing, affects their risks of developing breast cancer after sRT.
In this study researchers from the ICR, funded by Breakthrough Breast Cancer, The European Commission and the National Institute for Health Research, investigated 2,497 women treated with sRT for their Hodgkin lymphoma to determine whether the onset of their menstrual cycle or pregnancy affected their risk of developing breast cancer later in life.
Researchers linked a strong effect on the risk of breast cancer to the proximity of a woman’s sRT treatment to her first period. Women who received sRT treatment within six months of their first period were over 5.5 times more likely to get breast cancer than women whose treatment came more than 10 years after their first period.
Late onset period for women who undergo sRT was also a risk factor for breast cancer, but both a late-onset period and sRT treatment within two years of her first period was a particularly dangerous combination.
Women getting their first period at 16 were 2.5 times as likely to develop breast cancer as women whose first period was at 13, while women who started their periods later and also had sRT within two years of this time were 15 times more likely to develop breast cancer than women with earlier periods and sRT more than 10 years later.
However, the women in the study who became pregnant did not experience any extra risk of breast cancer due to their sRT treatment. Compared with women treated with sRT who did not get pregnant, the researchers found that full-term pregnancy led to a slight increase in risk, but giving birth before receiving sRT actually led to a drop in risk.
Professor Anthony Swerdlow, Professor of Epidemiology and member of the Aetiological Epidemiology Unit at The Institute of Cancer Research, said: “Because of the improved treatments for Hodgkin lymphoma over the past few decades more women are surviving for longer, only to develop secondary malignancies like breast cancer later on in their lives.
"Studies have shown that women who start their periods later are conferred some protection against breast cancer, but our research suggests the relationship between the age a woman starts her period and her breast cancer risk might be different for women who have undergone high doses of radiation than for the general population. But it is encouraging to find no significant effect of pregnancies before or after Hodgkin lymphoma on breast cancer risk.
"More work is needed to confirm our findings but these high risks should be considered when planning treatment and screening regimens for women diagnosed with Hodgkin lymphoma close to their period starting.”