Pregnancy-associated breast cancer and pregnancy following treatment for breast cancer, in a cohort of women from Victoria, Australia, with a first diagnosis of invasive breast cancer

Abstract

Background

This study examined pregnancy-associated breast cancer (PABC) and pregnancy following treatment for breast cancer.

Methods

We analysed data from a questionnaire-based, prospective study of women diagnosed with breast cancer. Timing of diagnosis in relation to pregnancy was self-reported in the enrolment questionnaire. Women reported subsequent pregnancies in annual follow-up questionnaires, up to at least 5 years from diagnosis.

Results

Women with PABC made up 3.3% of women <48 years at diagnosis and 14.3% of women aged <35 years at diagnosis. Nine of 46 (19.6%) women who were aged <40 years at diagnosis, and had either no children, or only one child, became pregnant subsequent to their diagnosis, and 8 experienced a live birth.

Discussion

As the number of women with PABC was small, conclusions from this study are limited. However, young women should be alert to PABC, especially in the post-partum period. Some women, with incomplete families at diagnosis, are choosing to have one or more pregnancies following treatment.

Introduction

The overall impact of pregnancy on the lifetime risk of breast cancer (BC) is considered to be protective, although protection may be limited to those women who were young at the time of their first completed pregnancy and those with hormone receptor positive disease.1, 2 In the short-term, pregnancy and the post-partum period are associated with an increased risk of BC. The period of increased risk has been estimated to range between 10 and 15 years following a first pregnancy in a young woman,³ to a period as long as 30–50 years for a woman whose first pregnancy occurs in her 30's,³ possibly explaining the difference in lifetime risk of BC in relation to age at first birth.⁴ Despite these protracted estimates of the duration of increased risk of BC following pregnancy, the definition of pregnancy-associated BC (PABC) is generally limited to BC diagnosed during, or within the 12 months following, pregnancy,3, 5, 6, 7 despite the suggestion that a longer time period should be used⁸ or that cancer which develops during lactation should be included, irrespective of the time that has elapsed since pregnancy.³

Given that the incidence of BC amongst young women is relatively low⁹ and that pregnancy is associated with an increase in risk, PABC has the potential to make an important contribution to all cases, in women of reproductive age.

Conversely, with women delaying childbearing,¹⁰ increasingly the diagnosis of BC is made in a woman who has either not completed, or in some cases, not even started her desired family. Although retrospective data suggest that pregnancy is safe after BC and may even lead to improved survival,11, 12 prospective studies are needed.13, 14

The Bupa Health Foundation Health and Wellbeing After Breast Cancer Study (Bupa Study) is a prospective questionnaire-based study of 1683 women diagnosed with their first episode of invasive BC between June 2004 and December 2006. In this report we have examined PABC as well as pregnancy following the treatment of BC, in women followed for nearly 6 years after diagnosis.