June 28th, 2012 by Hasham
Screening Guidelines: Breast Cancer
In 2008, approximately 184,450 new cases of breast cancer will be diagnosed in the US, with approximately 41,000 individuals dying from the disease. The average American woman has a one in seven chance of developing breast cancer during her lifetime.
Studies have shown that regular screening of women with no symptoms has decreased the number of women who die from breast cancer by approximately 45 percent.
In the past, recommendations for breast cancer screening have been the same for women from different cancer-risk groups. However, due to the results of recent studies, Memorial Sloan-Kettering investigators have developed separate breast cancer screening guidelines for women at average risk and for those at increased risk because of familial and genetic predisposition.
In the sections below, we include a discussion of different screening tests and our doctors’ breast cancer screening guidelines, separated into four distinct risk categories.
Breast Cancer Risk Types
Average-risk women have:
No history of invasive breast cancer (breast cancers that have spread beyond the milk ducts, or lobules), ductal or lobular carcinoma in situ (cancers that are confined to the milk duct or lobule), or atypia, which is also known as atypical hyperplasia (a form of benign breast disease)
No family history of breast cancer in a first degree relative (parent or sibling), or no suggestion/evidence of a hereditary syndrome
No history of mantle radiation (a radiation therapy used to treat Hodgkin disease)
Above-average-risk women have any of the following:
Family history of breast cancer (i.e. one first-degree relative — a parent or sibling — who had breast cancer)
Diagnosis of atypia, also known as atypical hyperplasia (a form of benign breast disease), or lobular carcinoma in situ (cancers that are confined to the milk duct or lobule)
History of having been treated with mantle radiation (a radiation therapy used to treat Hodgkin disease) before the age of 32
Breast Cancer Screening Tests
Breast cancer screening can involve a number of different types of examinations, which include breast self examination (BSE), clinical breast examination (CBE), mammography, magnetic resonance imaging (MRI), and ultrasound.
During a breast self-examination (BSE), a women checks her own breasts for any irregularities, which may include lumps, changes in breast size or shape, nipple discharge, or irregular tissue thickening. Despite attempts by investigators to demonstrate the impact of BSE on reducing breast cancer deaths, no study has been able to show a statistically significant reduction. As a result, our doctors and a number of national organizations no longer aggressively encourage women to perform BSE. However, because BSE is easy and free, and may detect some cancers, women are not discouraged from performing regular BSE.
Clinical Breast Examination
A clinical breast examination (CBE) is a physical examination of the breast performed by a health professional. In clinical studies where CBE was performed along with mammography, the reduction in deaths from breast cancer was similar to the reduction in those women who had received mammography alone. This suggests that CBE adds little to mammography in reducing breast cancer deaths.
Mammography is the diagnostic examination of the breast using low-dose x-rays. Annual mammogram screenings have been shown to reduce significantly the number of women dying from breast cancer in the age group 40 years and older. Until fairly recently, all mammograms used the conventional film-based technique, which utilizes x-rays to produce an image of the breast on film. Introduced in the US in 2001, digital mammography also uses x-rays but captures the image on a computer, where it can be viewed and manipulated for contrast. While finding no significant difference between the two techniques when applied to the general population and for most women over 50, studies have shown that digital mammograms detected more tumors in three specific groups: women under 50, women with dense breasts, and women not yet in menopause.
Ultrasound, also known as ultrasonography, is an imaging method in which high-frequency sound waves are used to create images of blood vessels, tissues, and organs including the breast. Breast ultrasound is often used to evaluate breast abnormalities that are found during mammography or a clinical breast exam. The accuracy of breast ultrasound is highly dependent on the skill level and training of the ultrasound technician. This creates an increased risk of false positives, requiring follow-up exams and biopsy — which can be expensive and lead to unnecessary anxiety for the patient.
Magnetic Resonance Imaging
Magnetic resonance imaging (MRI) is a diagnostic procedure that uses a magnetic field to provide three-dimensional images of internal body structures, including the breast. MRI is expensive and requires the injection of intravenous contrast dyes. Recent studies of women with an inherited risk of breast cancer have shown that MRI has a higher sensitivity in detecting breast cancers than other screening methods. However, there are no study data showing that MRI screening reduces the number of breast cancer deaths.
Summary of recommendations for clinicians and policy-makers
Recommendations are presented for the use of mammography, magnetic resonance imaging, breast self exam and clinical breast exam to screen for breast cancer. These recommendations apply only to women at average risk of breast cancer aged 40 to 74 years. They do not apply to women at higher risk due to personal history of breast cancer, history of breast cancer in first degree relative, known BRCA1/BRCA2 mutation, or prior chest wall radiation. No recommendations are made for women aged 75 and older, given the lack of data.
Breast Cancer Screening Recommendations for Women at Average Risk
Mammography is the most effective breast cancer screening tool used today. However, its benefits for women vary by age. The benefits of mammography in women ages 40-49; 50-69; and 70 and older are discussed below.
Figure 3.1 shows the screening recommendations for women at average risk of breast cancer from four major health organizations.
Mammography for women ages 50-69
For women ages 50 to 69, the life-saving benefits of mammography are clear. All women ages 50 to 69 should have regular mammograms (Komen recommends every year). This guideline is based on scientific evidence from randomized controlled trials done in the United States, Canada and Europe.
A meta-analysis that combined the results from seven randomized controlled trials found women aged 50 and older who got regular mammography had a 23 percent lower risk of dying from breast cancer than their peers who did not . More recent data suggest this benefit may be slightly lower. A 2010 study of women aged 50 and older who got regular mammography screening had a 10 percent lower risk of dying from breast cancer than their peers who did not get regular mammograms.