For many women, breast cancer is the disease they fear most. In fact, breast cancer is the most common cancer among women today. According to the American Cancer Society about 1.3 million women are diagnosed with breast cancer annually, and the disease accounted for more than half a million deaths worldwide in 2007. Over the last decade, however, death rates from breast cancer have declined or remained stable in most countries, due to medical advancements and increased public awareness, which have led to earlier diagnosis at stages where the cancer can potentially be cured.

Unlike lung cancer, for which smoking is the biggest and most powerful risk factor, there is no single factor that is responsible for the majority of breast cancers in women. Nevertheless, there are three factors which greatly increase a woman's risk of developing this disease: advancing age, a family history of the disease, and a personal history of breast cancer.

Fig.1: Illustration of breast tissue, showing milk ducts (dark blue), lobules (turquoise) and a breast tumor (yellow).

Breast cancer can occur in different forms

The first symptom, or subjective sign, of breast cancer is typically a lump that feels different than the surrounding breast tissue. Indications of breast cancer other than a lump may include changes in breast size or shape, skin dimpling, nipple inversion, or spontaneous single-nipple discharge.

Most breast masses are benign. They do not grow uncontrollably or invade other tissues, and are not life-threatening. In situ breast cancers are small nests of abnormal cells that are confined to the milk duct or lobule of the breast. Nearly all cancers at this stage can be cured. Invasive breast tumors spread to the surrounding healthy tissue and may metastasize to other parts of the body. The seriousness of invasive breast cancer is greatly influenced by its stage – the extent or spread of the cancer when it is first diagnosed.

Early diagnosis is decisive

The mainstays of early diagnosis are regular palpation (self-examination or by a gynecologist) and imaging procedures such as x-ray mammography, ultrasound, or magnetic resonance imaging (MRI). Most physicians regard x-ray mammography as a cornerstone for the detection of breast cancer at an early stage, even before subjective symptoms become evident. X-ray mammography is the only breast-imaging procedure approved for screening in the general population. Moreover, the technique is widely used for diagnostic and follow-up examinations of the breast, for guiding biopsy procedures, and for surgical planning and localization.

Several countries have implemented screening programs recommending x-ray mammograms for women between 40 and 69 years of age, with examinations to be taken every 1-2 years. Scientific studies suggest that the number of fatal carcinomas of the breast can be reduced by up to 30 percent using this method – provided that at least 70 percent of women make use of this offer.

X-ray mammograms – beneficial but not foolproof

X-ray mammography is highly accurate, but, like most medical tests, it is not perfect. Studies have shown that mammography may miss up to 35% of malignant cases, because it is typically less accurate in the denser breast tissue common in women before the menopause. Breast implants can also impede accurate mammogram readings, because both silicone and saline implants are not transparent for x-rays and can block a clear view of the tissues behind them. Moreover, about 5-10% of women have an abnormal or inconclusive mammogram which requires further testing. Most of these findings turn out to be benign after additional imaging studies and/or a biopsy.

Ultrasound imaging of the breast

An ultrasound examination (sonography) can be employed as an adjunct to x-ray mammography to follow up suspicious lesions. The technique helps to differentiate between benign cysts (cavities filled with liquid) and a lump of solid tissue. In the case of a cyst, no biopsy will be required for microscopic examination and further determination.

Magnetic resonance imaging

While normal mammography uses x-rays to generate images of the breast tissue, MRI uses radio waves. The patient lies on her stomach with both breasts hanging freely into a cushioned recess containing the signal receiver known as the breast coil. The entire bed on which the patient is lying moves into the MRI machine where the images are taken. MRI of the breast requires an intravenous injection of a gadolinium-containing contrast agent which helps to distinguish between a tumor and healthy tissue by lighting up its dense network of blood vessels. Bayer HealthCare Pharmaceuticals has long-standing experience in the development of MRI contrast media. In 1988, the company brought the first MRI contrast medium onto the market. Today, contrast agents have become indispensable in breast MRI.

Contrast-enhanced MRI adds sensitivity to breast imaging

MRI is considered to be particularly useful for women with a high risk of breast cancer and as a problem-solving tool in patients with dense breasts and inconclusive x-ray mammograms. Emerging data comparing MRI with other imaging modalities indicate that MRI is more sensitive than any other medical test in detecting breast cancer and is more accurate in characterizing the extent of the disease.

Although breast MRI has a reputation for providing a high rate of false positive findings, its specificity has improved considerably due to collective experience, the use of computer-aided diagnostic programs, and the implementation of the BI-RADS (Breast Imaging Reporting and Data System) lexicon for breast MRI established by the American College of Radiology.⁵

MRI screening – recommended for high-risk patients

In 2007, the American Cancer Society (ACS) released new guidelines recommending MRI screening in addition to mammography for women who meet at least one of the following conditions¹:

• Their life-time risk of breast cancer has been scored at 20%-25% or greater, based on family history and other factors.
• They carry mutations of the breast cancer genes BRCA 1 and 2.
• They have had chest-wall radiation treatment for cancers such as lymphoma at an early age.
• They (or their first-degree relatives) suffer from inherited syndromes (such as Li-Fraumeni and Cowden syndrome).

MRI in women suspected of having breast cancer

The American Society of Breast Disease (ASBD) as well as the European Society of Breast Imaging have endorsed the ACS guidelines.^2,3 Moreover, in its updated policy statement, the ASBD supports the diagnostic use of MRI in women with a high suspicion of breast cancer, particularly for:

• work-up of inconclusive clinical and imaging findings
• evaluating the integrity of breast implants and characterizing masses in women with breast augmentation
• detecting occult primary breast cancer in women presenting with axillary lymph node metastases
• local staging in women with newly diagnosed cancer
• monitoring the response to neoadjuvant chemotherapy

Fig. 2: Evaluation of a breast MR image

Searching for additional tumors in women with newly diagnosed breast cancer

For most breast cancer patients, the fear of a second cancer diagnosis is quite high. Up to 20% of women with breast cancer have another tumor in the same or opposite breast, even though nothing is found when they are checked with x-ray mammograms and physical examinations at the time of their original diagnosis. To provide the best service to the patient, every breast evaluation for cancer should include not only the affected breast, but also the contralateral breast. Studies have shown that MRI is capable of identifying the vast majority of contralateral cancers at the time of a woman's initial breast-cancer diagnosis. The resulting treatment at an early stage may spare patients another cancer diagnosis years after their initial treatment.

Breast cancer treatment and the use of MRI to monitor therapy

In recent years there has been an explosion of life-saving treatment advances for breast cancer. Treatment options include surgery, radiation, hormonal (anti-estrogen) therapy, chemotherapy and/or targeted therapies. No one treatment fits every patient, and a combination therapy is usually required. The choice is determined by many factors, including the age of the patient, menopausal status, the kind of cancer, its stage, and whether or not the tumor contains hormone receptors. Neoadjuvant chemotherapy, for example, is used in the treatment of unresectable breast cancer to reduce the tumor to a size that allows surgery. MRI has been shown to be superior to mammography and ultrasound in evaluating tumor response to neoadjuvant chemotherapy. Moreover, MRI may be considered after breast-conserving therapy to exclude a local recurrence of the tumor.

Taken together, breast MRI has attained a solid position in the diagnosis of suspected breast lesions. Moreover, MRI can save the lives of many high-risk women by catching cancers earlier.

References:

1. American Cancer Society Guidelines for Breast Screening with MRI as an Adjunct to Mammography, CA Cancer J Clin 2007; 57:75–89.
2. American Society of Breast Disease Policy Statement Use of Breast Magnetic Resonance Imaging (Breast MRI) in Breast Cancer Screening
3. Breast MRI: Guidelines from the European Society of Breast Imaging, Eur. Radiol. 2008 July; 18(7): 1307–1318.