At the ASCO 2017 meeting we presented the long-term results of our multi-centre study aiming to investigate the safety of having a pregnancy in patients with prior history of breast cancer and specifically in those with ER positive, oestrogen receptor positive, disease. We know that breast cancer is the most common tumour type in women of reproductive age and due to the current trend towards delayed childbearing many young breast cancer patient are diagnosed before the completion of their reproductive plan. We know from the literature that approximately half, 50%, of young breast cancer patients at the time of diagnosis will be interested to have a pregnancy after the end of treatment.
However, we also know that less than 10% of these patients actually manage to become pregnant and one of the main reasons for this low pregnancy rate in breast cancer survivors is the fact that still many physicians, and this has been shown also in recent surveys, believe that pregnancy in breast cancer survivors might have a detrimental prognostic effect, especially in patients with oestrogen receptor positive breast cancer. So this is the reason why we decided to update the results of our multi-centre, case-controlled study that had as its primary objective was really to look into the safety of having a pregnancy in patients with ER positive disease and the secondary objective in patients with ER negative breast cancer.
In the study we included 1,207 patients and out of these patients 333 had a pregnancy after breast cancer diagnosis and so were the cases included in the study. Approximately after ten years of median follow-up from initial breast cancer diagnosis we observed no difference in disease free survival and overall survival in patients with oestrogen receptor positive breast cancer between those who had the pregnancy after breast cancer and those without a subsequent pregnancy. When looking at the cohort of patients with ER negative disease we observed that there was no difference in disease free survival but the patients who had a pregnancy after breast cancer showed a significant 43% reduction in the risk of dying as compared to patients who did not have a pregnancy, so suggesting the safety of pregnancy in both patients with ER positive and ER negative disease.
If I could just clarify, the safety of pregnancy there is specifically for disease relapse not for any other consequence?
Yes, we evaluated the safety of pregnancy in terms of risk of disease recurrence, risk of dying and not the safety of pregnancy in terms of safety for the babies. These data were not available in the study, however we know from the literature that there is no higher risk of malformation in these children. The only slightly higher risk is of spontaneous abortion and pregnancy complications, for example pre-term delivery. So the main recommendation in breast cancer survivors who wish to have a pregnancy is to be followed more closely than healthy women without prior history of breast cancer. But it’s safe also for the babies.
The big question is what does that mean for patients, say, with breast cancer now who are going through it now but haven’t reached, like you say, that stage in their life where they are having families?
The main message is that pregnancy should be considered safe irrespective of ER status and so should not be discouraged. This is true also for patients with oestrogen receptor positive disease. In the specific cohort of patients with oestrogen receptor positive breast cancer these patients are candidates to receive five or up to ten years of adjuvant endocrine therapy and during this treatment pregnancy is contra-indicated during the adjuvant endocrine treatment. For specifically these patients there is currently ongoing worldwide a very important study called the POSITIVE study that is led by the International Breast Cancer Study Group. This study is currently investigating the safety of a temporary interruption, up to two years, of endocrine therapy in patients who wish to become pregnant for allowing them to try to become pregnant.