Breast cancer screening
Breast cancer screening is the medical screening of asymptomatic, apparently healthy women for breast cancer in an attempt to achieve an earlier diagnosis. The assumption is that early detection will improve outcomes. A number of screening tests have been employed, including clinical and self breast exams, mammography, genetic screening, ultrasound, and magnetic resonance imaging.
A clinical or self breast exam involves feeling the breast for lumps or other abnormalities. Medical evidence, however, does not support its use in women with a typical risk for breast cancer.
Universal screening with mammography is controversial as it may not reduce all-cause mortality and may cause harms through unnecessary treatments and medical procedures. Many national organizations recommend it for most older women. The United States Preventive Services Task Force recommends screening mammography in women at normal risk for breast cancer, every other year between the ages of 40 and 74. Other positions vary from no screening to starting at age 40 and screening yearly. Several tools are available to help target breast cancer screening to older women with longer life expectancies. Similar imaging studies can be performed with magnetic resonance imaging but evidence is lacking.
Earlier, more aggressive, and more frequent screening is recommended for women at particularly high risk of developing breast cancer, such as those with a confirmed BRCA mutation, those who have previously had breast cancer, and those with a strong family history of breast and ovarian cancer.
Abnormal findings on screening are further investigated by surgically removing a piece of the suspicious lumps to examine them under the microscope. Ultrasound may be used to guide the biopsy needle during the procedure. Magnetic resonance imaging is used to guide treatment, but is not an established screening method for healthy women.
Breast exam
Breast examinations are highly debated. Like mammography and other screening methods, breast examinations produce false positive results, contributing to harm. The use of screening in women without symptoms and at low risk is thus controversial.A 2003 Cochrane review found screening by breast self-examination is not associated with lower death rates among women who report performing breast self-examination and does, like other breast cancer screening methods, increase harms, in terms of increased numbers of benign lesions identified and an increased number of biopsies performed. They conclude "at present, breast self-examination cannot be recommended". Another study done by the National Breast Cancer Foundation states that 8 out of 10 lumps found are noncancerous.
On the other hand, Lillie D. Shockney, a Professor from Johns Hopkins University states, 'Forty percent of diagnosed breast cancers are detected by women who feel a lump, so establishing a regular breast self-exam is very important.'
There are different tactics on how to go about examining one's breasts. Doctors suggest that you use the pads of your three middle fingers and move them in circular motions starting at the center of the breast and continuing out into the armpit area. Apply different amounts of pressure while conducting the exam. Any lumps, thickenings, hardened knots, or any other breast changes should be brought to the attention of your healthcare provider. It is also important to look for changes in color or shape, nipple discharge, dimpling, and swelling.
Mammography
is a common screening method, since it is relatively fast and widely available in developed countries. Mammography is a type of radiography used on the breasts. It is typically used for two purposes: to aid in the diagnosis of a woman who is experiencing symptoms or has been called back for follow-up views, and for medical screening of apparently healthy women.Mammography is not very useful in finding breast tumors in dense breast tissue characteristic of women under 40 years. In women over 50 without dense breasts, breast cancers detected by screening mammography are usually smaller and less aggressive than those detected by patients or doctors as a breast lump. This is because the most aggressive breast cancers are found in dense breast tissue, which mammograms perform poorly on. The European Commission's Scientific Advice Mechanism recommends that MRI scans are used in place of mammography for women with dense breast tissue.
The presumption was that by detecting cancer in an earlier stage, women will be more likely to be cured by treatment. This assertion, however, has been challenged by recent reviews which have found the significance of these net benefits to be lacking for women at average risk of dying from breast cancer.
Mechanism
Screening mammography is usually recommended to women who are most likely to develop breast cancer. In general, this includes women who have risk factors such as having a personal or family history of breast cancer or being older women, but not being frail elderly women, who are unlikely to benefit from treatment.Women who agree to be screened have their breasts X-rayed on a specialized X-ray machine. This exposes the woman's breasts to a small amount of ionizing radiation, which has a very small, but non-zero, chance of causing cancer.
The X-ray image, called a radiograph, is sent to a physician who specializes in interpreting these images, called a radiologist. The image may be on plain photographic film or digital mammography on a computer screen; despite the much higher cost of the digital systems, the two methods are generally considered equally effective. The equipment may use a computer-aided diagnosis system.
There is considerable variation in interpreting the images; the same image may be declared normal by one radiologist and suspicious by another. It can be helpful to compare the images to any previously taken images, as changes over time may be significant.
If suspicious signs are identified in the image, then the woman is usually recalled for a second mammogram, sometimes after waiting six months to see whether the spot is growing, or a biopsy of the breast. Most of these will prove to be false positives, resulting in sometimes debilitating anxiety over nothing. Most women recalled will undergo additional imaging only, without any further intervention. Recall rates are higher in the U.S. than in the UK.
Effectiveness
On balance, screening mammography in older women increases medical treatment and saves a small number of lives. Usually, it has no effect on the outcome of any breast cancer that it detects. Screening targeted towards women with above-average risk produces more benefit than screening of women at average or low risk for breast cancer.A 2013 Cochrane review estimated that mammography in women between 50 and 75 years old results in a relative decreased risk of death from breast cancer of 15% and an absolute risk reduction of 0.05%. However, when the analysis included only the least biased trials, women who had regular screening mammograms were just as likely to die from all causes, and just as likely to die specifically from breast cancer, as women who did not. The size of effect might be less in real life compared with the results in randomized controlled trials due to factors such as increased self-selection rate among women concerned and increased effectiveness of adjuvant therapies. The Nordic Cochrane Collection reviews said that advances in diagnosis and treatment might make mammography screening less effective at saving lives today. They concluded that screening is "no longer effective" at preventing deaths and "it therefore no longer seems reasonable to attend" for breast cancer screening at any age, and warn of misleading information on the internet. The review also concluded that "half or more" of cancers detected with mammography would have disappeared spontaneously without treatment. They found that most of the earliest cell changes found by mammography screening should be left alone because these changes would not have progressed into invasive cancer.
The accidental harm from screening mammography has been underestimated. Women who have mammograms end up with increased surgeries, chemotherapy, radiotherapy and other potentially procedures resulting from the over-detection of harmless lumps. Many women will experience important psychological distress for many months because of false positive findings. Half of suspicious findings will not become dangerous or will disappear over time. Consequently, the value of routine mammography in women at low or average risk is controversial. With unnecessary treatment of ten women for every one woman whose life was prolonged, the authors concluded that routine mammography may do more harm than good. If 1,000 women in their 50s are screened every year for ten years, the following outcomes are considered typical in the developed world:
- One woman's life will be extended due to earlier detection of breast cancer.
- 2 to 10 women will be overdiagnosed and needlessly treated for cancer that would have stopped growing on its own or otherwise caused no harm during the woman's lifetime.
- 5 to 15 women will be treated for breast cancer, with the same outcome as if cancer had been detected after symptoms appeared.
- 500 will be incorrectly told they might have breast cancer.
- 125 to 250 will undergo breast biopsy.
- For women in their 40s: About 2,000 women would need to be screened every year for 10 years to prevent one death from breast cancer. 1,000 of these women would experience false positives, and 250 healthy women would undergo unnecessary biopsies.
- For women in their 50s: About 1,350 women would need to be screened for every year for 10 years to prevent one death from breast cancer. Half of these women would experience false positives, and one-quarter would undergo unnecessary biopsies.
- For women in their 60s: About 375 women would need to be screened for every year for 10 years to prevent one death from breast cancer. Half of these women would experience false positives, and one-quarter would undergo unnecessary biopsies.