Chapter 27: Breast Cancer

INTRODUCTION

Breast cancer is the most common malignancy in women worldwide and is also the most frequent tumor during pregnancy.¹ While some of these cancers are linked to genetic aberrations (and require genetic counseling), they are most frequently sporadic. The diagnosis and management of breast cancer become more challenging in premenopausal women, when fertility preservation issues come into play for women who have not yet completed childbearing age. Although advances have been made in reproductive medicine, the cancer and its treatment may limit its use. Oncofertility issues need to be addressed and dealt with from the beginning of the oncological approach to maximize opportunities for obtaining a successful breast cancer outcome and, simultaneously, fertility preservation. Breast cancer occurring during pregnancy demands a multidisciplinary approach to address the health of both the mother and the fetus.

EPIDEMIOLOGICAL RISK FACTORS FOR BREAST CANCER IN PREMENOPAUSAL WOMEN

Nearly 7% of breast cancer cases are diagnosed in women younger than 40 years. In this age group, breast cancer constitutes almost half of all cancer cases.^2,3 The main risk factors recognized for this cancer are genetic alterations, environmental factors, and obesity and lifestyle habits. Table 27-1 illustrates some of the established epidemiological factors and the strength of the increment in relative risk their presence confers.⁴

The preeminent risk factor for breast cancer is genetic inheritance of a mutation in the BRCA1 or BRCA2 gene.^5,6 These are high-penetrance susceptibility genes located on the long arms of chromosomes 17 and 13, respectively.^5,7 One mutated copy of either gene suffices to generate the hereditary breast and ovarian cancer syndrome, which is transmitted in an autosomal-dominant pattern.⁶ The proteins coded by the BRCA1 and BRCA2 genes are implicated in the homologous recombination repair of DNA double-strand breaks, an essential mechanism for maintenance of genome integrity.^6,8 Besides predisposing patients to early-onset breast cancer and increasing risk of ovarian cancer, the hereditary breast and ovarian cancer syndrome also confers higher risk of developing pancreatic cancer, fallopian tube tumors, and uterine and ...