- What is the purpose of breast cancer screening?
Breast cancer screening uses several available tools to find breast cancer in the earliest possible stage among women who have no breast complaints.
- What are the tools used for breast cancer screening?
CBE and screening mammography. Breast self-examination is recommended for women 20 years of age or older. The monthly BSE should be performed after each period in young women and at a fixed time of each month after menopause. While some large randomized studies did not find any benefit of regular breast self-examination, a lump detected by BSE may prompt women to seek needed professionals evaluation.
The clinical breast examination is performed by a physician. The effectiveness of CBE alone in detecting early breast cancer has not been studied, but it is believed that CBE as an adjunct to screen mammography can assist to accurately detect breast cancer at early stage.
Mammography is an x-ray imaging of the breasts. While clinical breast examination may detect tumors that are less than 1 cm (smaller than a half inch), mammography may detect a mass as small as several millimeters as well as small calcium deposits that are not readily palpable. Literature shows that screening mammography may detect a lesion up to three years before it can be felt upon self or clinical examination. Screening mammography has a proven value of reducing breast cancer mortality in women 50 years of age and older. Better detection is expected with the use of improved technologies such as digital mammography. Recently, a national study that included investigators at UCLA analyzed data from more than 42,000 patients and showed that digital mammography is more effective in women younger than 50 years of age, in postmenopausal women with dense breast tissue and in perimenopausal women.
It is important to keep in mind that screening tests do not prevent breast cancer. These tests are intended to find cancer at the earliest possible stage when it is the most treatable and likely to be cured.
- Who should be screened for breast cancer?
The American Cancer Society recommends that in addition to regular breast self-examination, women who are 20 years of age or older should receive a clinical breast examination by their doctor every three years. Screening mammography should be started at age 40 and done annually.
- What are the current recommendations for breast cancer screening?
It is important to learn from your primary care doctor or other healthcare practitioner how to do your own breast self-examination. If you are a pre-menopausal woman, the best time to do breast self-examination is around five days after the start of your period. If you are post-menopausal, it is advised that you do breast self-examination on the same day of each month.
CBE is recommended every three years for women between 20 and 40 years old, and annually thereafter.
Mammography should be performed annually starting at age 40. When applicable, earlier mammography films should be made available to the radiologist for comparison with new mammography films. It is not clear what is the upper limit of age for routine mammography screening in women with reasonable health.
- Are the screening recommendations the same for women with a very strong family history of breast cancer?
Women with a strong family history of breast cancer, or who have family members who are known carriers of BRCA-1 or -2, benefit from a more intense screening schedule that includes an earlier start of screening and shorter screening intervals for clinical breast examination and mammography. Women with strong family histories of breast cancer also may need additional tests such as ultrasound or MRI (magnetic resonance imaging). The baseline mammography may be started in these women at age 25. The exact age for starting screening mammography depends on the youngest individuals in the families who are affected by breast cancer. It is uncertain how frequently the screening mammography should be performed in women in their 20s and 30s.
- What are BRCA-1 and BRCA-2?
BRCA-1 and BRCA-2 are two genes that may be mutated in families with multiple members who are affected by breast and ovarian cancers. Mutations of these genes can be identified by a blood test. Carriers can pass the mutated genes to both daughters and sons. Women with proven BRCA-1 or -2 mutations have an approximately 85 percent chance of developing breast cancer and an approximately 50 percent chance of developing cancer in both breasts. The onset of breast cancer in these women can be years younger than those without these mutations. Men with BRCA-2 mutation also have a significantly increased risk of developing breast cancer. Individuals with BRCA mutations may develop multiple types of cancers.
- What factors are associated with an increased risk for breast cancer?
Many risk factors have been identified that affect one's chance of developing breast cancer. The followings are considered as risk factors for breast cancer:
- Being female. Females are 100 times more likely to get breast cancer than males.
- Age. The risk of breast cancer increases with age.
- Hormonal factors. Several hormonal factors increase the risk for breast cancer, including early onset of first menstrual period (before age 12); late menopause (after age 55); first full-term pregnancy after age 30; and hormone replacement therapy after menopause depending on dosage, duration of treatment and type of hormone combination.
- Family history. Women with multiple family members with breast and/or ovarian cancer, first-degree relatives with breast cancer, family members with breast cancer diagnosis at young age are at greater risk for breast cancer. It must be noted that approximately 85 percent of women with breast cancer have no significant family history of breast cancer, and only 10 percent of all breast cancers are hereditary disease.
- Genetic factors. Known genetic factors such as BRCA-1 and/or -2 mutations, familial cancerous syndromes put women at higher risk.
- Dietary factors. Although studies have been inconclusive, it has been suggested that early age of exposure to alcohol and significant alcohol intake are potential risk factors. The effect of fat intake on breast cancer risk is inconclusive. Weight gain in post-menopausal women has been correlated with increased chance of developing breast cancer.
- Activity level. A sedentary lifestyle may contribute to the risk for breast cancer.
- Radiation exposure. Ionizing radiation, especially single large-dose exposures for women with previous history of Hodgkin's lymphoma treated with radiation at a young age, or other types of radiation exposure at young age, may be a contributing risk factor.
- Personal history. A personal history of lobular carcinoma in situ (LCIS) and atypical hyperplasia, ovarian and/or endometrial cancer, and invasive breast cancer or precancerous condition (DCIS) are contributing factors.
Raquel Prati, M.D. and Helena Chang, M.D, Ph.D.