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MUNEEZA KHAN, MD, AND ANNA CHOLLET, MD, MPH

This is a corrected version of the article that appeared in print.

Am Fam Physician. 2021;103(1):33-41

Patient information: See related handout on mammogram screening for breast cancer, written by the authors of this article.

 This clinical content conforms to AAFP criteria for CME.

Author disclosure: No relevant financial affiliations.

Breast cancer is the most common nonskin cancer in women and accounts for 30% of all new cancers in the United States. The highest incidence of breast cancer is in women 70 to 74 years of age. Numerous risk factors are associated with the development of breast cancer. A risk assessment tool can be used to determine individual risk and help guide screening decisions. The U.S. Preventive Services Task Force (USPSTF) and American Academy of Family Physicians (AAFP) recommend against teaching average-risk women to perform breast self-examinations. The USPSTF and AAFP recommend biennial screening mammography for average-risk women 50 to 74 years of age. However, there is no strong evidence supporting a net benefit of mammography screening in average-risk women 40 to 49 years of age; therefore, the USPSTF and AAFP recommend individualized decision-making in these women. For average-risk women 75 years and older, the USPSTF and AAFP conclude that there is insufficient evidence to recommend screening, but the American College of Obstetricians and Gynecologists and the American Cancer Society state that screening may continue depending on the woman's health status and life expectancy. Women at high risk of breast cancer may benefit from mammography starting at 30 years of age or earlier, with supplemental screening such as magnetic resonance imaging. Supplemental ultrasonography in women with dense breasts increases cancer detection but also false-positive results.

Breast cancer is the most common nonskin cancer in women and accounts for 30% of all new cancers in the United States.1 From 2001 to 2016, more than 2.3 million women in the United States were diagnosed with breast cancer.2 The incidence of breast cancer increases after 25 years of age, peaking between 70 and 74 years.2 Approximately one in eight women will develop invasive breast cancer (12.8% lifetime risk).1
Clinical recommendationEvidence ratingComments
The USPSTF and AAFP state that there is insufficient evidence regarding the benefits and harms of breast self-examination and therefore recommend against teaching patients to perform it. The ACS encourages breast self-awareness and recommends against breast self-examination because of a lack of evidence regarding improved outcomes.26,27,31 CConsensus expert opinion; lack of evidence supporting breast self-examination
The USPSTF recommends biennial screening mammography for average-risk women 50 to 74 years of age; the AAFP supports this recommendation.26,29 BMeta-analysis of eight randomized trials; other organizations recommend considering annual screening
The American College of Obstetricians and Gynecologists recommends that women 75 years and older be involved in shared decision-making for screening mammography that is based on health status and life expectancy. The ACS and National Comprehensive Cancer Network recommend screening after 75 years of age if life expectancy is at least 10 years, and the American College of Radiology recommends continued screening if life expectancy is at least five to seven years.3,30,31,33 CConsensus expert opinion; the risks vs. benefits in this age group have not been well-studied
RecommendationSponsoring organization
Do not routinely use breast magnetic resonance imaging for breast cancer screening in average-risk women.Society of Surgical Oncology
Do not perform screening mammography in asymptomatic patients with normal examination findings who have less than a five-year life expectancy.American Society of Breast Surgeons – Benign Breast Disease
Do not recommend screening for breast cancer if life expectancy is estimated to be less than 10 years.Society for Post-Acute and Long-Term Care Medicine
Do not recommend screening for breast, colorectal, prostate, or lung cancers without considering life expectancy and the risks of testing, overdiagnosis, and overtreatment.American Geriatrics Society

WHAT'S NEW ON THIS TOPIC
Breast Cancer Screening
A 2016 meta-analysis calculated that per 10,000 women screened with mammography, three breast cancer deaths are avoided over 10 years in women 40 to 49 years of age, eight deaths are avoided in women 50 to 59 years, 21 deaths are avoided in women 60 to 69 years, and 13 deaths are avoided in women 70 to 74 years. [corrected]
One out of every eight women 40 to 49 years of age who has a screening mammogram will subsequently undergo additional imaging, and for every case of invasive breast cancer detected by screening mammography in this age group, 10 women will have had a biopsy.
In a large, multicenter trial, women with dense breasts and a negative standard mammogram result had two-year screening with MRI or standard mammography. The interval cancer rate was lower in the MRI group than in the mammography group; however, MRI had a high false-positive rate with hundreds of negative breast biopsy results among the 4,738 women who underwent MRI screening.
MRI = magnetic resonance imaging.

The overall mortality rate in U.S. women with breast cancer is about 20 per 100,000. Mortality rates are highest in women 85 years and older (170 per 100,000).2 White women have the highest rate of breast cancer diagnosis, whereas Black women have the highest rate of breast cancer–related death.2 Breast cancer is also the most common cause of cancer-related death in Hispanic women and the second leading cause of cancer-related death behind lung cancer among all women.2
Cancer screening recommendations are determined by the patient's current anatomy. Transgender females with breast tissue and transgender males who have not undergone complete mastectomy should receive screening mammography based on guidelines for cisgender persons (see https://www.aafp.org/afp/2018/1201/p645.html#sec-4).

What Are the Risk Factors for Breast Cancer?

The strongest risk factors are a history of childhood chest radiation, older age, increased breast density, family history of breast cancer, and certain genetic mutations (Table 1).3–16 However, most women who develop invasive breast cancer do not have any of these risk factors.3
FactorRisk of breast cancer (relative risk unless otherwise noted)
BRCA mutations by age group
20 to 29 yearsBRCA1: 106, BRCA2: 46
30 to 39 yearsBRCA1: 44, BRCA2: 38
40 to 49 yearsBRCA1: 15, BRCA2: 13
50 to 59 yearsBRCA1: 8.2, BRCA2: 9.8
60 to 69 yearsBRCA1: 2.8, BRCA2: 2.1
History of chest radiotherapy
OverallSIR = 21.9
Whole lung radiationSIR = 43.6
Patient age
Age ≥ 65 years vs. < 65 years> 4.0
Breast density
≥ 75%4.64
50% to 74%2.92
25% to 49%2.11
5% to 24%1.79
< 5%1.0
History of breast cancer
First-degree relative with breast cancerHR = 1.61; OR = 1.64
Personal history of breast cancer1.42
Benign breast disease
Proliferative disease with atypia3.93
Proliferative disease without atypia1.76
Nonproliferative disease1.17
Age at menopause
45 to 49 years0.86
≥ 55 years1.12
Age at menarche
11 years1.09
15 years0.92
Reproductive history
Nulliparity1.0
First pregnancy at 35 years1.16
First pregnancy at < 30 years0.73
Hormone therapy
1 to 4 years of combined estrogen/progestin1.60
1 to 4 years of estrogen only1.17
5 to 14 years of combined estrogen/progestin2.08
5 to 14 years of estrogen only1.33
Other
Obesity (body mass index > 30 kg per m2)1.48
Moderate alcohol consumption1.1

EVIDENCE SUMMARY

A retrospective cohort study demonstrated a standardized incidence ratio (i.e., the ratio of observed to expected number of cases) of 21.9 for breast cancer in women who received chest radiation during childhood.4 Higher doses of radiation were associated with higher risk, and the highest risk was in those who received whole lung radiation (standardized incidence ratio = 43.6). The overall cumulative risk of developing breast cancer by 50 years of age was 30%.4
Increasing age is another strong risk factor. Invasive breast cancer will be diagnosed in one out of 42 women 50 to 59 years of age, and this rate increases to one out of 14 in women 70 years and older.5
Breast density is the amount of glandular and stromal tissue compared with adipose tissue shown on a mammogram. A systematic review and meta-analysis found that compared with women who do not have dense breasts, the relative risk of developing breast cancer is 1.79 for women with breast density between 5% and 24% and 4.64 for those with breast density of 75% or higher.6
Data from the Breast Cancer Surveillance Consortium and the Collaborative Breast Cancer Study showed that having a first-degree relative with breast cancer increases a woman's personal risk by a hazard ratio of 1.61 and odds ratio of 1.64.7 For patients with BRCA mutations, the risk of developing breast cancer by 80 years of age is 60% to 63%, regardless of family history.8
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