We present here at the IMPAKT conference some research on breast cancer in pregnancy. This is an ongoing registration study since 2003 and we have about 1,700 patients registered in this registry. We have also collected biomaterial from those patients. This research started two years back and we had about 150 patients with biomaterial, that means tissue from patients who were diagnosed and treated with breast cancer during pregnancy. From those patients finally 100 could be evaluated for mutations in the tissue. So we did an NGS panel on those materials from paraffin embedded tissue and compared the mutational landscape in these patients with data from the TCGA dataset.
What were your findings?
First of all, the main aim was to look if the biology of breast cancer diagnosed during pregnancy is different from others. We could not really answer this question completely because our patients were much younger than the TCGA dataset. From a first look at the cohorts younger than 45 years in the TCGA dataset and comparing that with ours we found that the PI3 kinase mutations were much lower in our dataset and the p53 mutations were much higher. This is contrast to the TCGA data and this is in contrast what we found. One explanation might be that the biology is more aggressive, this would support that we have more p53 mutations. Another difference could be that the age which is driving the breast cancer during pregnancy patients with a median age of below 35 and the TCGA data where the patients were not that young, with a median age of about 40, was also an explanation for that.
We split the patients by hormone receptor status and found that the hormone receptor negative there were really no difference between the breast cancer in pregnancy cohort and the TCGA dataset. But when we looked at the hormone receptor positive cohort, again this was evident that the main difference was in the PI3 kinase mutations and the TP53 mutations where the results are just described – less PI3 kinase and more TP53 mutations.
Now we are looking further into this difference – is this a real biology difference? Is this a difference based on the different methodology used to sequence the tumours? Is it a difference because we used FFP and the TCGA used fresh frozen? So there are variants but it could also be that the biology in these patients is a little bit different because the patients are so much younger. But this is work still to be done.
What is the clinical significance of the treatment of breast cancer in pregnant women?
The patients with breast cancer during pregnancy are treated as closely as possible to the general guidelines for young breast cancer patients because we need absolutely to avoid an under-treatment of those patients. So, in general, we can operate those patients at any time during the pregnancy and after the first trimester, which is around the 14th gestational week, we can also start giving them chemotherapy, the standard chemotherapy. What is more problematic is giving anti-HER2 treatment because there are cases that patients suffer from a severe oligo- and anhydramnios, so the amniotic fluid is gone or is decreasing substantially. There were also foetal deaths reported but it was never clear it was really related to the anti-HER2 treatment during given pregnancy or if this event would anyway have happened. But for the moment we recommend not to treat those patients unless there is real urgency and a highly aggressive breast cancer.
What we also postpone until after surgery is the endocrine treatment if the patient has a hormone receptor positive tumour and radiotherapy which is usually indicated in all patients with breast conserving therapy and in some patients with mastectomy.
What would be your take home message?
The main message is if you have a patient treated with breast cancer during pregnancy try to register them in the GBG database as far as possible. You can contact us, you’ll find the information on the website, GBG.de. We need to learn more about those patients; new drugs are coming up so we need to update our recommendations as the standard recommendations of how to treat our breast cancer patients in general need to be updated.
