Breast cancer and pregnancy

The frequency with which breast cancer is diagnosed in pregnant women is low (in the region of 1 in 1000 pregnancies), but the management of these women presents a considerable challenge to those involved in their care. Women frequently present with tumours displaying adverse pathological prognostic features. Initial investigation may be carried out as for non-pregnant women, but with particular attention paid to the risks of exposure to the foetus of ionizing radiation.

Surgery can be carried out with seemingly little increased risk to the mother or foetus, but radiotherapy is usually avoided. In terms of short-term complications chemotherapy may be given relatively safely when administered outside of the first trimester and not around the time of delivery. However, the principle concern with all of these interventions is what the long-term implications for the newborn might be.

Introduction

It has been estimated that up to 3% of breast cancers may be diagnosed in women who are pregnant or lactating.1 However, there is an increasing trend in many developed countries for women to delay childbearing until later in life, and this incidence may therefore rise. The management of these women presents a considerable challenge to those involved in their care. This is partly due to the rarity of the association, and partly because, in contrast to other areas of breast cancer oncology, we do not have large randomized trials to guide our clinical practice. We are forced to rely on assumptions and anecdotes, and that it is a difficult scenario to work in, particularly when the stakes (both medical and emotional) are so high. In this review, the basic principles underlying the management of pregnant women with cancer will be discussed, before moving on to discuss pregnancy-associated breast cancer in more detail.

Principles underlying the oncological management of pregnant women

The first stage of foetal development is implantation, which occurs within 2 weeks post-conception. Physical or pharmacological insults during this period may precipitate foetal loss. Following this, over the next 8 weeks of foetal development, is the period of organogenesis. At the end of this period, despite the tiny size of the foetus (approximately 3 cm) all of the major organ systems have been developed. Insults during this period may manifest themselves as major malformations. However, after this period, because organogenesis is complete, major malformations are unlikely to occur. This does not mean that the foetus if free from risk of harm, it still needs to grow and mature, and be safely delivered. Moreover, some organ systems, such as the gonads and central nervous system continue to develop later through foetal life. However, the greatest risks of harm, and particularly the risks of major malformation are over by the completion of the first trimester.