Women who are diagnosed with breast cancer in the 12 months after they have completed a pregnancy are 48% more likely to die than other young women with breast cancer according to new research to be presented at the seventh European Breast Cancer Conference (EBCC7) in Barcelona.

However, the study of 2,752 breast cancer patients by Australian researchers found that if the breast cancer was diagnosed while the women were pregnant, their risk of dying was nearly the same as other, non-pregnant women diagnosed with breast cancer - only three percent higher.

Assistant Professor Angela Ives, a research fellow at The University of Western Australia, told the conference that the findings suggest that the cumulative effect of pregnancy may play a role in breast cancer prognosis and this, along with whether a woman breast feeds, needs further investigation.

However, she said: "It is important to stress that our findings should not discourage women from breast feeding as we know that this is beneficial to both mother and baby in a number of ways. While most breast symptoms or abnormalities identified in young women are benign, it is important that when a woman is pregnant or breastfeeding any symptoms or abnormalities are not assumed to be due to the pregnancy or breastfeeding, particularly if the symptoms persist. It is important that both health professionals and young women are breast aware, even during pregnancy and breastfeeding, and promptly have symptoms investigated to allow early diagnosis.

"For women who are diagnosed with breast cancer after pregnancy, they and their clinicians may wish to consider different forms of treatment to improve survival."

Prof Ives said that because very little is known about gestational breast cancer, she and her colleagues decided to find out more so that women could make informed choices about their breast cancer management and pregnancy outcome.

Using the Western Australia Data Linkage System, they identified a group of 2,752 women, aged less than 45, diagnosed with breast cancer in Western Australia between January 1982 and December 2003. They followed them to December 2007 or to their date of death, if earlier.

"The WA Data Linkage System is one of only five comprehensive record linkage systems in the world. It brings together population-based hospital morbidity data, birth and death records, mental health services data, cancer registrations and midwives' notifications, linked back to 1980. In this case we have been able to identify all cases of gestational breast cancer diagnosed in WA and all other cases of breast cancer in similar aged women to identify what is different about them," she said.

The researchers took account of additional factors such as age at diagnosis, histological tumor grade, stage of disease and whether the cancer had spread to the lymph nodes. From the total number of women, 182 were diagnosed with gestational breast cancer, 55 while they were pregnant and 127 after the end of the pregnancy. Prof Ives found that, as might be expected, histological tumor grade, disease stage and lymph node involvement were all associated with a worse survival for all the women. The finding of the increased risk of death if breast cancer was diagnosed after pregnancy remained after adjusting for lymph node status, disease stage at diagnosis, histological tumor grade and age.

Prof Ives said: "It has been assumed over many years that actually being pregnant at diagnosis led to poor survival, but this study has shown that it might be the amount of time that a woman is pregnant and her body's responses to being pregnant that encourage the growth of a breast cancer. Another explanation might be that the changes in the breast while pregnant and then breastfeeding mask a breast cancer, which is, therefore, more advanced when it is diagnosed. It could be a combination of both. In addition, we do know that pregnancy and breastfeeding reduce the long-term risk of a woman developing breast cancer, but we also know that, in the short term, having been pregnant may increase the risk of developing breast cancer. There needs to be further research into these possible explanations for our findings."

Another study presented at EBCC7 found that women who have been treated for breast cancer can choose to become pregnant and have babies, without fears that pregnancy could put them at higher risk of dying from their cancer. In a meta-analysis of 14 trials researchers from Belgium and Italy found that, not only was pregnancy safe for breast cancer survivors, but, in fact, it could improve their chances of survival.

Breast cancer is the most common cancer for women during their childbearing years. As women delay starting a family until they are older, and the survival from breast cancer has improved, increasing numbers of breast cancer survivors want to have babies after their cancer treatment has finished. Until now, it was unclear whether it was safe for them to do so, due to concerns that the hormonal changes associated with pregnancy, in particular the increase in estrogen, could prompt the cancer to recur or become more aggressive.

Dr. Hatem A. Azim, Jr., a Fellow at the Department of Medical Oncology at the Institute Jules Bordet (Brussels, Belgium), and colleagues in Italy analyzed results from 14 trials that had taken place between 1970 and 2009, involving 1,417 pregnant women with a history of breast cancer and 18,059 women with a history of breast cancer who were not pregnant.

They found that patients who became pregnant following a diagnosis of breast cancer had a significant reduction of 42% in the risk of death compared to breast cancer survivors who did not get pregnant.

Dr. Azim said: "Our findings clearly demonstrate that pregnancy is safe in women with history of successfully treated breast cancer. There is a wide perception in the oncology community that women with history of breast cancer should not get pregnant for fear of pregnancy increasing the risk of recurrence by means of hormonal stimulation. This meta-analysis strongly argues against this notion.

"Now we are refining the results by analyzing subgroups to examine the effect of the timing of pregnancy - for instance how soon after a breast cancer diagnosis is it safe to become pregnant - and differences in survival according to the patient's age, lymph node status and so on.

"It is still common that patients are faced with incorrect counseling regarding pregnancy and the chances of future fertility following the end of breast cancer treatment and, thus, they are denied the chance of getting pregnant. Nowadays, there is a rising trend of delaying pregnancy to later in life and more young women are cured from breast cancer. So it is important to provide high level of evidence to help physicians in counseling these patients. This work may result in improving the quality of life of millions of young women who finish their adjuvant breast cancer therapy and want to get pregnant."

Dr. Azim said there might be a number of explanations related to hormones or the immune system as to why pregnancy seemed to confer a protective effect on breast cancer survivors.

"It is well known that estrogen is associated with breast cancer development. However, beyond a certain level, estrogen exerts inhibitory effects on breast cancer cells. Laboratory experiments have shown that estrogen and progesterone receptors located on 60-70% of breast tumors undergo apoptosis when exposed to high levels of estrogen, which possibly mimics levels encountered during pregnancy. Furthermore, prolactin is elevated in pregnancy and there is evidence suggesting that women with high levels of prolactin have a reduced risk of breast cancer relapse." He added: "Nevertheless, hormonal changes during pregnancy are very complex, and the effect seen in this study could possibly be the result of the interaction of the different hormones rather than an action of a particular one by itself.

"Immunological theories could partially explain the possible protective value of pregnancy as well. It has been shown that fetal antigens are expressed on the tumor cells of the mother. Thus, antibodies produced by the mother in response to these antigens, may act as a kind of tumor vaccination."

Dr. Azim said that they had contacted all the authors of trials published after 1995 to get extra information on subgroups, and this would inform their further research.

He concluded: "Nowadays, fertility after cancer has become a top issue not only for patients, but also physicians. In 2006, the American Society of Clinical Oncology published guidelines that state that fertility issues should be discussed with patients before treatment - a recommendation we believe is of great importance."