Major Finding: Risk of death rose 48% when women were diagnosed with breast cancer within the 12 months after a pregnancy.
Data Source: 2,752 breast cancer patients at one center in Australia.
Disclosures: Dr. Ives and Dr. Saunders reported no conflicts of interest. Financial support for the research was provided by Susan G. Komen for the Cure and the Australian National Breast Cancer Foundation.
BARCELONA — Women younger than 45 years are 48% more likely to die if they are diagnosed with breast cancer in the first 12 months after completing a pregnancy than are other young women who are diagnosed with breast cancer and are not pregnant.
In a study of 2,752 breast cancer patients who were seen at the University of Western Australia in Crawley, Dr. Angela Ives and associates also found that there was a small (3%), but nonsignificant rise in the risk of death in women who were diagnosed with breast cancer when still pregnant.
“A possible explanation of this is that the total time a woman is pregnant, with or without lactation, correlates with increased growth of a breast cancer, and this can lead to worse survival,” Dr. Ives, a research fellow at the university, said at the European Breast Cancer Conference.
Gestational breast cancer was defined in this study as breast cancer that was diagnosed during pregnancy or in the 12-month postpartum period. “Completing pregnancy” included live births, terminations, and miscarriages.
In addition to pregnancy status, the researchers examined the effects of a variety of factors that could affect survival in the women studied. These included age at diagnosis, histologic tumor grade, disease stage, lymph node status, and length of survival and death status (as of Dec. 31, 2007, when the data were censored).
As expected, young age, positive lymph nodes, higher disease stage, and histologic tumor grade at diagnosis were associated with poor prognosis.
“When we looked at pregnancy status, those who were pregnant when they were diagnosed [n = 55] had similar survival outcomes to all those young women who had no associated pregnancy [n = 2,570],” Dr. Ives reported. “Those that were diagnosed in the first 12 months post partum [n = 127], after they completed a pregnancy, however, were 48% more likely to die than the women who were pregnant at their diagnosis.”
Dr. Ives noted that a Norwegian registry study had recently reported similar results, although in that study the postpartum period was defined as up to 6 months after completion of pregnancy (J. Clin. Oncol. 2009;27:45–51).
“Based on this research, there are two things that we would like to see happen in research, so that we can better inform women and their treating clinicians,” Dr. Ives said.
“The first is to look at how the time that a woman is pregnant or breastfeeding impacts on their survival,” she added. This would involve looking at the effects of pregnancy on survival from the time of conception to the time of breast cancer diagnosis.
“We'd also like to look at how pregnancy affects breast cancer cells,” Dr. Ives said. In the long term, pregnancy and breastfeeding are known to be protective against being diagnosed with breast cancer, she noted, but in the short term, it seems that is not the case and that it actually might increase the chances of being diagnosed with breast cancer.
Dr. Christobel Saunders, coauthor of the study and professor of surgical oncology at the university, commented that the study's findings do not change how women should currently be advised. She explained that the subjects were already diagnosed with breast cancer, and that the study did not look at possible causal or treatment effects.
“There's an intriguing biological question now which needs to be further explored about what it is about the length of pregnancy and/or breastfeeding, or perhaps the way that the body accommodates the tumor and allows a more aggressive tumor to develop,” Dr. Saunders said.