by Julian Dollente, RN and Christopher M. Cirino, DO MPH
Breast cancer has become a global health issue, as it is the leading cause of cancer-related deaths among women worldwide. In 2020 alone, about 2.3 million women were diagnosed with breast cancer, with 680,000 deaths worldwide. 7.8 million women received this diagnosis in the past five years, making it the world’s most prevalent cancer.
From the 1930s through the 1970s, breast cancer mortality has remained the same, partly due to late diagnosis. Improvements in survival began in the 1980s following early detection programs and treatment modalities.
Thanks to the establishment of screening practices and therapeutic advances, breast cancer prognosis is generally more favorable in early and asymptomatic stages. The 5-year survival rate of patients with breast cancer is above 80% due to early detection. However, the survival rate remains low in developing countries, such as in Africa (40%), where screening is not widespread.
The article will outline the breast cancer risk factors and screening options.
Table of Contents
What is Breast Cancer Screening?
Screening means looking for something before any signs or symptoms emerge. The goal is to detect a malignancy early enough to make it more easily treatable.
Doctors try to understand better which women are more likely to get breast cancer by looking at their age, family history, and specific exposures during their lifetime. With the help of this information, they can recommend when to begin screening, which tests to use, and how often.
Who Is at Risk for Breast Cancer?
Almost half of the breast cancers develop in women with no other identifiable risk factors besides gender and age over 40 years.
The female gender contributes the most to risk. Breast cancer occurs at a rate of 100 times higher in women than in men. The higher risk is primarily due to the hormone estrogen, which stimulates breast development and can contribute to breast cancer growth.
Regarding age, 99.3% of all breast cancer-associated deaths were in women older than 40.
Other factors increase the risk of breast cancer, including:
- Harmful use of alcohol
- Family history of breast cancer
- History of radiation exposure
- Reproductive history (age of menarche and age at first pregnancy)
- Tobacco use
- Postmenopausal hormone therapy use
Breast Cancer Screening Recommendations
There has long been a debate about when to start screening for breast cancer. Several organizations issue screening guidelines, and some of these are different. The concerns regard early detection, mortality reduction, and overdiagnosis with unnecessary worry and procedures. These risks factor into recommendations of beginning age, frequency of screening, and modality used.
More recently, cancer screening trials suggest a benefit to screening at a younger age to detect cancer earlier. The UK AGE randomized controlled trial (2020) found a utility of breast cancer screening in women aged 40-40 years compared to those not screened. The study of over 160 thousand women followed for ten years showed a benefit in earlier screening, with a 25% reduction in mortality (Duffy et al., 2020). The study did not determine a significant risk of overdiagnosis in screening at an earlier age.
The American College of Radiology developed a process known as the Breast Imaging Reporting and Data System (BI-RADS). Radiologists provide a BIRADS score to indicate risk of the mammogram findings and when repeat screening should be considered. The table below identifies the categories (source: radiopaedia).
BI-RADS 0: Incomplete, need further imaging
BI-RADS 1: negative
BI-RADS 2: benign
BI-RADS 3: probably benign (<2% probability of malignancy); short interval follow-up suggested
BI-RADS 4: suspicious for malignancy (2-94% probability); low-, medium-, and high- further classified.
BI-RADS 5: highly suggestive of malignancy
BI-RADS 6: known biopsy-proven malignancy
Breast Cancer Screening Tests
There are several studies available.
Here are examples of screening tests, including other exams you can take to detect breast cancer early:
A mammogram is an x-ray of the inside of the breast and is the most common screening test for breast cancer. A mammogram can detect tumors that are too small to feel by hand. It may also detect ductal carcinoma in situ (DCIS) — abnormal cells lining the breast duct that may become invasive cancer in some women. The overall sensitivity of a mammogram is about 87%, meaning it will miss cancer in some women. BI-RADS scores can provide some follow-up recommendations.
There are three types of mammogram tests:
- Film mammography – an x-ray picture of the breast
- Digital mammography – a computer picture of the breast
- Digital breast tomosynthesis (DBT) – A series of x-rays of the breast from different angles made into 3-D images using a computer.
Tumors are less likely to be found in women with dense breast tissue using mammography because both tumors and dense breast tissue appear white in mammogram results. That is why mammograms are not recommended in younger women, as they tend to have dense breast tissue.
Several factors affect the ability of mammography to detect breast cancer, including:
- Age and weight of the patient
- Size and type of tumor
- Location of tumor formation in the breast
- Sensitivity of breast tissues to hormones
- The density of breast tissue
- Timing of the test within the woman’s menstrual cycle
- Quality of mammogram picture
- Radiologist’s interpretation skill
Breast Magnetic Resonance Imaging (MRI)
A breast MRI uses magnets, radio waves, and computers to improve the resolution of breast imaging. Additionally, it does expose a person to radiation as a mammogram would.
MRI is not the recommended method for screening someone with an average risk of cancer. Doctors reserve this for women at high risk for breast cancer. Factors that put women at high risk include:
- Specific gene changes (changes in BRCA1 or BRCA 2 genes)
- Family history (first-degree relative with breast cancer)
- Certain genetic syndromes (Li-Fraumeni or Cowden syndrome)
An MRI is more sensitive than mammography but more likely to have false-positive test results, such as detecting non-cancerous breast masses. Additionally, unlike mammography, it does not show microcalcifications, calcium deposits that can signal an early malignancy.
However, Breast MRI may supplement standard screening modalities in some women.
The following are other screening tests that are currently under clinical trials:
- Breast Exam
A clinical breast exam is an examination of the breast by a doctor or other health professional who uses their hands to feel for lumps or other changes. There is no conclusive evidence to support that having a clinical breast exam decreases the chances of dying from breast cancer.
Both women and men may do breast self-exams to check their breasts for lumps or any irregularities. Consult your doctor if you feel any lumps or notice any changes to your breast. Nevertheless, similar to clinical exams, regular breast self-exams do not show a benefit in cancer mortality.
Thermography is a procedure that records the temperature of the skin that covers the breast using a heat-sensing infrared camera. Abnormal tissue growth or tumors can cause temperature changes that may show up on the thermogram.
3. Tissue Sampling
Breast tissue sampling is a procedure to take cells and view them under a microscope. Again, breast tissue sampling as a screening test hasn’t shown a mortality benefit.
Breast Cancer Screening: Benefits vs. Harms
Every screening test has benefits and harms. The primary use of screening tests is finding cancer early when it is easier to treat. Indeed it is crucial to detect cancers at an earlier stage before they metastasize. The 5-year survival rate drops from 99% to 28% from localized to metastatic breast cancer.
Every screening test comes with some harm. These are worth discussing with your doctor before the study to prepare you for the possibility of further testing.
To give you an idea, here are some of the harms of mammography:
False-positive test results
Breast cancer screening tests are not 100% accurate, and results may appear abnormal even though no cancer is present. The problem with a false-positive test result is that it can lead to more expensive, invasive, time-consuming tests and may cause anxiety.
False-positive test results are more common in the following:
- Younger women (under age 50)
- Women who had prior breast biopsies
- Women with a family history of breast cancer
- Women who take hormones for menopause
The false-positive mammography and biopsy rates were higher in annual screening than biennial (61% vs. 42%; 7% vs. 5%, respectively. (Nelson, 2016). Denser breast tissue also exposed women to a higher rate of additional tests and procedures. Nevertheless, there is a 4 to 6-fold higher risk of breast cancer in women with denser breast tissue compared to less dense. The risk comes with densities greater than 75% compared to 10% or less as determined on mammography (percent mammographic density) (Boyd, 2013).
Abnormal mammograms require further studies to rule out cancer. Tests lead to anxiety, even in false positives. One study found that recall for further testing was associated with borderline or clinically significant anxiety in most women (70%) (Kitano, 2015).
Tests may also lead to overdiagnosis, as some breast cancers found only by mammogram screening may never develop into a life-threatening disease. When these cancers are detected, doctors may initiate treatment that causes severe side effects and may not lead to a longer, healthier life.
Exposure to radiation
Mammography exposes your breasts to low doses of radiation. The radiation exposure of women who start getting mammograms after age 50 is less likely to cause them any harm. However, women with large breasts or breast implants may be exposed to slightly higher doses of radiation while having mammogram screening.
Pain, Discomfort, and Anxiety
During a mammogram, the technician places your breasts between two plates and presses them down to help get a better x-ray image. The pressure may cause temporary pain and discomfort for some women. The amount of pain does depend on the phase of your menstrual cycle and your general tolerance level.
Summing It Up
“An ounce of prevention is better than a pound of cure.”Benjamin Franklin
Early breast cancer detection can make a difference between surviving or dying from cancer. While advanced treatments improve breast cancer prognosis, they may not be as effective in later stages of the disease.
While it is clear that breast cancer screening is beneficial, it is not without risks. Before you get screened, it is helpful to review the steps and what further screening looks like with your doctor.
Boyd N. Mammographic density and risk of breast cancer. An Soc Clin Oncol Educ Book. 2013. doi:10/1200/EdBook_AM.2013.33.e57.
Duffy S, et al. Annual mammographic screening to reduce breast cancer mortality in women from age 40 years: long-term follow-up of the U.K. Age RCT. Health Technol Assess. 2020. 24(55):1-24. doi:10.3310/hta24550.
Kitano A, et al. Psychological impact of breast cancer screening in Japan. 2015. Int J Clin Oncol. 20(6):1110-6. doi: 10.1007/s10147-015-0845-0. Epub 2015 May 26.
Nelson H, et al. Harms of Breast Cancer Screening: Systematic Review to Update the 2009 U.S. Preventive Task Force Recommendation. Ann Intern. Med. 164(4):256-67. doi: 10/7326/M15-0970. Epub 2016 Jan 12.
Here is a Breast Cancer Risk Assessment Tool.