Breast Cancer Screening: Saving Women’s Lives
Breast cancer screening saves women’s lives. Almost a third of all cancers diagnosed in women worldwide are breast cancers. It is also among the deadliest; only lung cancer causes more deaths among women.
In the USA alone, 250,000 women are diagnosed with breast cancer each year, and 42,000 women die of it.
Screening and early diagnosis are the foremost tools in our effort to reduce the impact of breast cancer. Early diagnosis has several advantages: less extensive surgery, simpler chemotherapy and radiotherapy, and better survival.
What is Breast Cancer Screening?
Breast cancer screening is a plan for women to attend a health care facility at regular intervals. At these times, a provider will carry out screening tests that detect cancer before they are large enough to be felt.
This early diagnosis is the crux of screening. Cancers that have grown enough to be felt are usually late-stage (advanced breast cancer). Such cancers require extensive surgery, and aggressive chemotherapy and radiotherapy.
Breast cancers start as small growths. As they grow, cancer cells spread through the body (metastasis). The first spread is usually to the lymph nodes in the armpit. Later, the cancer may involve the liver, lungs, bones, skin, brain, and other organs.
Advanced, widespread cancer is challenging to treat. Outcomes after late diagnosis are much worse than after early diagnosis.
Advantages of Breast Cancer Screening
Survival in breast cancer depends on the stage when treatment is started. Cancer diagnosed before there is any spread has a five-year survival of 99%.
Women who attend screening regularly have significantly lower chance of being diagnosed with late-stage cancer. They’re also far more likely to be offered breast-conserving surgery, since their cancers are small and early-stage.
The most important advantage is mortality, of course. Regular breast cancer screening saves lives.
How is Breast Cancer Screening Done?
The well-known methods are breast self-examination, clinical breast examination (by a health care professional), and imaging. Imaging can be:
- Magnetic resonance imaging (MRI)
- Ultrasonography (also called ultrasound)
- Digital breast tomosynthesis (DBT).
If the screening tests show any abnormality, further testing is advised. Depending on the abnormality seen, there could be a recall for diagnostic mammography, a repeat imaging after six months, or a diagnostic biopsy.
Imaging can diagnose breast cancers much before clinical examination or self-examination can. Because of this, breast self-examination and clinical examination are not the recommended methods for early diagnosis of breast cancer now.
Mammography is an x-ray of the breasts that shows cancerous growths. It uses lower doses of radiation than regular x-rays. It is, thus, appropriate for frequent use.
Mammograms are a mature technology, and very effective at finding breast cancers early. There is adequate evidence that mammography saves women from dying of breast cancer. It is estimated that regular screening of 10,000 women in their sixties will save 21 lives over ten years.
A mammography report may state that the breasts are dense. It means only that the proportion of glandular and fibrous tissue to fat is higher than average.
Dense breasts are not abnormal. However, the likelihood of cancer is higher, and mammography is often unable to detect the growths.
These women are often diagnosed with advanced breast cancer (ABC). Alternative methods are required not to miss an early stage cancer. DBT, MRI, and ultrasound are the additional methods available.
Digital Breast Tomosynthesis
DBT (also called 3D mammography) is an imaging method recommended for women with dense breasts to improve the diagnosis of any growth. It reduces the recall rates by allowing more definitive diagnoses.
DBT is not used routinely as it has about twice the radiation exposure of regular mammography.
Ultrasonography is used if the mammogram is inconclusive. It is especially valuable in women with dense breasts.
Lumps that can be felt but are not seen on mammography are also evaluated by ultrasound. It can also differentiate masses that are fluid-filled (cysts; not usually feared) and those that are solid (which might be cancer).
An ultrasound is not painful, is widely available, and has no radiation exposure.
Magnetic resonance imaging uses magnets and waves to make detailed pictures. It is valuable when the mammogram is unclear. MRI has better detection rates than DBT and does not use ionizing radiation.
It is also used in women who have already been diagnosed to have breast cancer. It gives a detailed picture of the size and spread.
MRI not recommended as an initial screening tool because it is too sensitive. It detects too many growths that are not cancerous, leading to needless worry, testing, and treatment.
Women who are at high risk for breast cancer are sometimes advised MRI for screening, in addition to mammography. MRI cannot replace mammography, because it misses some growths that the latter identifies.
What is a Breast Biopsy?
If mammography or other imaging shows significant abnormalities, a biopsy is required. A biopsy is a procedure to obtain tissue from the suspicious area of the breast for examination by a pathologist.
A biopsy is recommended when one of the following are seen:
- A solid or indeterminate mass
- Distortion of the normal breast architecture
- A complex cyst
- Microcalcification (tiny deposits of calcium).
The biopsy is done under mammography, ultrasound, or MRI guidance. This ensures that the tissue sample is taken from the right part of the breast.
Examination of the tissue sample under a microscope after special staining and processing enables a pathologist to diagnose or rule out cancer.
Types of Breast Biopsy
FNA (fine needle aspiration): A thin needle is inserted into the area of suspicion, and a syringe is used to suck (aspirate) some cells for examination.
Core needle biopsy: A larger needle is used to get a core of tissue from a growth seen on imaging or felt on examination. A better sample of tissue is obtained, and is usually preferred for cancer diagnosis.
Surgical (open) biopsy: A part or all of the lump is removed by making an incision. If cancer is strongly suspected, the surgeon removes the entire growth along with a surrounding margin of normal tissue.
The choice of biopsy depends on the size, position, number, and type of the growth(s), and other risk factors, if any.
When Should Screening be Done?
The U.S. Preventive Services Task Force (USPSTF) recommends that women start breast cancer screening at age 50 years and have it every two years. It advises women over 40 to talk to their doctors and make individualized decisions about mammography.
The American Cancer Society recommends that women have annual screening starting at age 45 years, and change to biennially (every two years) at age 55 years.
Other expert groups give recommendations different from these. It is important to realize that all guidelines recommend screening to save women from dying of breast cancer. The differences are in the age of starting screening and the frequency.
When is Screening Most Advantageous?
The most common age for diagnosis of breast cancer is 64 years. The benefits of regular mammography are highest for those 60-69 years old.
Women in their fifties also benefit significantly by attending screening regularly.
Women Aged 40-49
These women have a low incidence of breast cancer, and do not benefit as much from screening. Their risk of overdiagnosis and overtreatment are high.
They have a large proportion of false -positive screening results — suspicious findings on screening that turn out to be non-cancerous on diagnostic imaging or biopsy.
Obviously, these false-positive results are associated with significant anxiety and unnecessary testing. For this reason, breast cancer screening is not recommended for women in their forties, or is recommended only in the latter half of that decade.
Should Women in Their Forties Never Start Screening?
Some women are at high risk for breast cancer, by reason of family history (sibling, parent, or child with breast cancer), genetic mutation, or another factor that increases their risk (Read also: At High-Risk for Breast Cancer? Your Options).
These women should discuss the decision to start screening early with their doctor.
Risk Factors for Breast Cancer
Age. Women over 50 are at higher risk.
Family history. A close family member having breast cancer increases the risk.
Longer reproductive period. Early onset of periods and a late menopause prolong the exposure to hormones.
Earlier events. Breast cancer before, or some non-cancerous breast diseases, increase the risk of breast cancer.
Radiation treatment. Exposure of the chest or breasts to radiation therapy (for example, for lymphoma) increases the risk.
Drugs. DES (diethylstilbestrol) was used to prevent miscarriage. We now know it increases the breast cancer risk both for the woman who took it and her daughter.
Familial syndromes. Some inherited syndromes are associated with high probability of breast cancer.
Women with more than one risk factor may be advised to start breast cancer screening early, sometimes as early as thirty years.
When Should Regular Screening Stop?
Age 74. Beyond this age, there is no evidence that early detection of breast cancer carries any benefit.
Who Shouldn’t Have Breast Cancer Screening?
Women under the age of forty with no risk factors. Routine screening detects few tumors, and leads to a large number of unnecessary biopsies and other investigations.
Older women. Even if small breast cancers are found, most of them are unlikely to grow, spread, or become life-threatening. These women are likely to die of other causes.
Women with other diseases who do not have long to live. Finding breast cancers will not prolong life and will cause stress and reduced quality of life.
Pregnant women. The dose of radiation is small, but x-rays are avoided during pregnancy for fear of harming the fetus.
Imaging is very capable, and detects a lot of tumors while they’re small. In most cases, this prevents the growth and spread of cancer. Aggressive surgery and chemotherapy are avoided, and survival rates are better.
Some of these small tumors never grow, spread, or threaten life. There is, at present, no way to differentiate these non-threatening growths from the dangerous ones. For safety, all found tumours are treated.
The identification and treatment of such tumors is called overdiagnosis and overtreatment. Most estimates put the occurrence at 1% to 10%.
The Harms of Screening
Mammography is a very sensitive tool and detects a large number of masses. Most of them turn out to be harmless, but cause enormous anxiety to women and their families.
Overdiagnosis and overtreatment are significantly more frequent when screening is started early and performed more frequently. Reducing the frequency of screening to biennially reduces these hazards considerably, while maintaining the beneficial effects.
Breast cancer screening is a powerful part of our armamentarium in our quest to preserve health, increase lifespans, and improve the quality of life. Like all potent weapons, it must be used with expertise and sound judgement to deliver the best results.
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5. Screening for Breast Cancer: U.S. Preventive Services Task Force Recommendation Statement
6. Trimboli et al. Do we still need breast cancer screening in the era of targeted therapies and precision medicine?