Breast Cancer

BREAST CANCER

Deborah Wechter, MD

Virginia Mason Medical Center (Seattle, WA)

Breast cancer is the most commonly occurring cancer in women and will affect one in nine women in their lifetime. The cause of the majority of breast cancers is unknown though risk factors which may be associated with the development of breast cancer include early age with first menstrual period, late age at menopause, late first pregnancy, nulliparity, no breastfeeding, and a family history of breast or ovarian cancer.

Only 5-10% of breast cancers are hereditary. There are two gene mutations, BRCA1 and BRCA2, which increase the lifetime risk of breast cancer up to 85% and ovarian cancer as high as 60% in affected women. Women (or men) who might be at risk of having a genetic mutation include those with:

Early onset breast cancer

Two primary breast cancers

Family history of early onset breast cancer

Personal or family history of male breast cancer

Personal or family history of ovarian cancer

Ashkenazi Jewish heritage

Known BRCA mutation in the family.

In BRCA carriers, one of the options for prevention is prophylactic bilateral mastectomy. If not done, follow-up should include yearly mammogram, yearly breast MRI and twice yearly clinical breast exam. Prophylactic oophorectomy reduces the risk of ovarian cancer, and also reduces the risk of developing breast cancer by 50% in premenopausal women. Tamoxifen may also decrease the risk of breast cancer.

Screening for breast cancer includes breast self exam (BSE), clinical breast exam (CBE), and mammography. Although BSE is widely recommended, there is actually no compelling evidence to show that BSE affects prognosis. Although some women find it reassuring to become familiar with their breast exam, others may find it intimidating to try to assess a breast abnormality. Performing BSE is a personal choice that should be discussed with a woman’s primary care provider. CBE is recommended by the American Cancer Society every 3 years for women in their 20’s and 30’s, and annually for asymptomatic women who are 40 and older. Screening mammography is recommended yearly for women 40 and older by the American Cancer Society. Screening breast MRI is reserved for women with a high lifetime risk of breast cancer and guidelines for its use have been published by the American Cancer Society (cancer.org; CA Cancer J Clin 2007;57:75-89).

If a breast mass is found on exam, mammogram and ultrasound may be used to assess the mass. If a mammogram is abnormal, additional mammographic views and ultrasound may be used. If exam or imaging is suspicious, the preferred method of diagnosis is core needle biopsy which is performed under local anesthesia by a breast radiologist or surgeon using mammogram, ultrasound or palpation for guidance.

Once a diagnosis of cancer is made, a multidisciplinary team including providers with expertise in radiation oncology, medical oncology, breast surgery, plastic surgery, and genetic counseling guides evaluation and treatment.

The clinical stage of the tumor is based on tumor size, lymph node status, and presence or absence of metastases. Lab tests and imaging such as chest x-ray, breast MRI, PET/CT scan, bone scan, and CT scan are chosen to help define the stage based on NCCN guidelines (cancer.org).

Surgical options for treatment of the breast are partial mastectomy (lumpectomy) and mastectomy. Partial mastectomy is usually performed as an outpatient procedure and involves removing the cancer with a rim of normal tissue around it. If the mass is not palpable, either wire localization with mammogram or ultrasound, or ultrasound alone, identifies the cancer for the surgeon. With wire localization, a mammogram or ultrasound is performed to identify the cancer and a skinny wire is inserted through a needle toward the cancer under local anesthesia. In the operating room, an incision is made using the wire as a guide and the cancer is removed with a rim of normal breast tissue around it. An x-ray is taken of the tissue to prove the cancer has been removed and that there is a clear margin.

A mastectomy removes the entire breast and nipple-areolar complex, but not the muscle underlying the breast. A skin-sparing mastectomy removes the entire breast and nipple, but leaves a small rim of skin around the nipple, allowing more skin to be used in reconstruction. Reconstruction by a plastic surgeon can be performed at the same time (immediate) or at any point in the future (delayed).  The two primary options include implant reconstruction, or autologous reconstruction using one’s own tissue from the abdominal wall, buttock or back.

One of the first places that breast cancer can spread is to the lymph nodes under the arm. With invasive cancer, the lymph nodes are assessed with sentinel lymph node biopsy (SLNB) unless the lymph nodes have already been shown to have cancer by biopsy or imaging. This technique removes the first node or nodes draining the cancer through microscopic lymph channels from the breast to the axillary nodes. To find the sentinel node, a small amount of radioactive tracer is injected into the breast using local anesthesia the afternoon before or the day of the operation. In the operating room, sometimes a blue dye is injected into the breast as well. The radioactive or blue sentinel node is removed using a gamma probe (a small Geiger counter) and evaluated by the pathologist. If the sentinel node has cancer, an axillary node dissection may be performed. This involves removal of the lower level lymph nodes in the fatty tissue under the arm.

Additional treatment after operation may include radiation therapy, chemotherapy and hormonal therapy. Women who undergo partial mastectomy also require radiation treatment to the breast to reduce the risk of recurrence. Without radiation, the chance of cancer coming back in the breast may be up to about 30%, though with radiation the risk is at most up to 10-15%. Whole breast radiation begins a few weeks after operation and is given over approximately 6 weeks for a few minutes each weekday. A newer technique called accelerated partial breast radiation may be appropriate in selected patients. It is not yet considered the standard of care because we do not know that the long term risk of breast recurrence is as low as with whole breast radiation. The area of cancer is treated twice daily for five consecutive working days using external beam radiation, placement of an intracavitary balloon catheter (MammoSite®), or, least commonly, insertion of interstitial wires through the breast tissue. Some women will require radiation therapy after mastectomy to reduce the risk of chest wall recurrence if the invasive cancer is 4 cm or larger in size, if there are 4 or more lymph nodes involved with cancer, or if the cancer is close to the skin or chest wall.

The use of hormonal therapy may be considered in women whose tumors test positive for estrogen and/or progesterone receptors depending upon tumor size, lymph node status, and other factors. These oral medications are usually taken for up to 5 years.

The primary purpose of chemotherapy is to treat or prevent metastasis (spread to lymph nodes, liver, lung, bone or other organs). Recommendations are based on tumor size, lymph node status and other factors such as age and coexisting medical conditions. Chemotherapy is usually given intravenously every one to three weeks for a period of 3-6 months. In women with “HER-2 positive” tumors, Herceptin (trastuzumab), a monoclonal antibody, may be considered for treatment. HER-2/neu is a tumor oncogene that is “overexpressed” or positive in some tumors.