Over the past few decades the incidence of breast cancer has increased; however, mortality related to breast cancer is on the decline. This has been attributed to early detection and more effective treatment options.1 In the United States, a woman’s lifetime risk of developing breast cancer is estimated at 12.3%, based on the Gail model risk assessment criteria.1 Risk stratification has been pivotal in assessing risk of developing breast cancer. It identifies those women at normal risk compared with those women with high risk factors. Risk of developing breast cancer is increased per the following criteria:
• Prior therapeutic thoracic irradiaton or mantle irradiation;
• Age 35 years or older with a 5-year risk for invasive breast carcinoma of 1.7% or greater;
• A lifetime risk for breast cancer greater than 20%, based on models largely dependent on family history;
• A strong family history or genetic predisposition for the disease; Lobular carcinoma in situ (LCIS) or atypical hyperplasia; and
• Prior history of breast cancer.2
Risk assessment, using the modified Gail model, assesses the risk for invasive breast cancer as a function of current age, age at menarche, age at first live birth or nulliparity, number of first-degree relatives with breast cancer, number of previous benign breast biopsies, atypical hyperplasia in a previous breast biopsy, and race.2 However, the list of risk factors that predispose a woman to breast cancer should include pregnancy.
The incidence of breast cancer during pregnancy is expected to increase as a result of the cultural trend of having children later in life. Breast cancer is diagnosed in pregnant women in approximately 1 in 3,000 pregnancies.3,4 Statistics demonstrate that approximately 10% of patients younger than 40 years with a new diagnosis of breast cancer are pregnant.3 Given that clinicians in oncology and obstetrics have never had to speak the same language in terms of patient management, the increasing incidence of breast cancer during pregnancy is shifting this paradigm. The delay of childbearing until after age 30 years is a major factor in the increasing incidence of pregnancy and breast cancer.2 Of great importance for nursing across the two disciplines is that care for the pregnant woman with breast cancer differs significantly from care for the nonpregnant woman with breast cancer. A greater understanding of the true biology and nature of breast cancer in pregnancy is needed to maximize the care of these women and reduce the health risks for both the mother and the fetus.
INCIDENCE AND PREVALENCE
Cancer is the second most common cause of death in women of reproductive age, and accounts for 33% of maternal deaths during pregnancy.3 Pregnancy-associated breast cancer is defined as breast cancer during pregnancy and up to 1 year postpartum.5 Six million pregnancies occur in the United States annually, and of these pregnancies, approximately 4,058,000 result in a live birth.3 Although often considered rare, breast cancer is the most common cancer in pregnant and postpartum women, after cervical cancer, with an average age of 32 to 38 years at the time of diagnosis.3,4,5 Worldwide, approximately 30,000 cases of breast cancer are diagnosed in pregnant women annually, and an estimated more than 40,000 women were affected in 2009 alone.5,6
In comparison with nulliparous women, the risk for a woman to develop breast cancer is increased in the years immediately following pregnancy, whereas all parous women, regardless of age, have higher incidence of breast cancer compared with nulliparous women.6 This risk is known to exist for a minimum of 10 years and increases up to 15 years after birth in women younger than 25 years at the time of delivery.7 For years, the cross-over effect has been that women who have children at a younger age have a protective benefit as it relates to the risk of breast cancer. Age as a major risk factor for pregnancy-associated breast cancer is consistent throughout the evaluation of women who develop the disease during pregnancy. Women who are uniparous and complete their first pregnancy before age 25 years do still possess transient risks, but their overall lifetime risk of developing the disease is reduced by at least 36%.7 A critical point for pregnancy-associated breast cancer increases at age 35 years, as full-term pregnancy is associated with a permanent increase in breast cancer risks from this age on.6