The American College of Physicians (ACP) now recommends mammography every two years for asymptomatic, average‑risk women aged 50 to 74. The new guideline has been published in the Annals of Internal Medicine.

The change is intended to reduce harms from over-testing, but some specialists warn it could delay diagnosis in younger women and those with dense breasts. The guidance affects millions of screening decisions and may change how doctors and patients discuss breast cancer screening.

Breast cancer is the most commonly diagnosed cancer in women in the United States, accounting for roughly 30% of new female cancer cases each year. On average a woman in the US has about a 1 in 8 lifetime risk of developing breast cancer; the median age at diagnosis is 62.

Likewise, breast cancer is the most common cancer among women in Malaysia and the cancer rates are rising. In 2016 report, the age-standardized incidence rate stood at 34.1 per 100,000 women—an increase from previous years. More worrying is the early onset of the disease: 13.6% of women diagnosed are under 40, a stark contrast to just 5% in Western countries.

In Malaysia, according to the Malaysian Ministry of Health (MOH) Clinical Practice Guidelines (2019/2020), mammogram screening is recommended biennially (every 2 years) for average-risk women aged 50 to 74 years, which is in line with the new guidance. Women aged 40–49 years are usually considered moderate‑risk and may start annual mammograms, depending on local risk‑assessment practice and individual factors.

Screening with mammography aims to detect cancer before symptoms appear, when treatment is most likely to be successful.

However, screening can cause harms including false positives, unnecessary biopsies, anxiety, and overdiagnosis — detection of cancers that would not have caused symptoms or shortened life.

What the new guidance says

The ACP’s updated statement recommends biennial screening mammography for asymptomatic (without symptoms) women at average risk aged 50 to 74.

For women aged 40 to 49 it advises shared decision‑making between clinician and patient, taking into account individual risk, values and preferences but generally women aged 40–49 years are usually considered moderate‑risk and may start annual mammograms.

For people aged 75 and older, or with limited life expectancy, the ACP recommends discussing whether to stop routine screening.

For women with dense breasts (BI‑RADS C or D), the statement suggests clinicians may consider digital breast tomosynthesis (DBT, often called 3D mammography) but does not recommend adding routine ultrasound or MRI for average‑risk women with dense tissue. Always talk to your healthcare providers for medical advice.

What the evidence behind the guidance shows

The ACP drew on clinical guidelines and systematic evidence reviews from national and international guideline developers. The key points cited are:

• Biennial screening produces similar mortality benefit to annual screening in average‑risk women over 50 but leads to substantially fewer false‑positive recalls and biopsies.
• In women aged 40–49 the absolute mortality benefit is small and uncertain; screening at these ages increases false positives and overdiagnosis. Hence decisions should be personalised.
• Continued routine screening after 74 has not shown clear mortality benefit and increases additional testing and overdiagnosis.
• DBT can improve cancer detection and reduce recall rates compared with standard 2D mammography, particularly in dense breasts, but supplemental MRI or ultrasound is not routinely recommended for average‑risk women with dense tissue.

How it works

Screening mammography detects tumours by imaging breast tissue and flagging suspicious areas for further tests. Increasing the frequency of screening raises the chance of detecting cancer earlier but also increases the number of false alarms.

A false positive is an imaging result that looks suspicious but turns out not to be cancer; it can lead to more imaging, needle biopsies and psychological distress.

Overdiagnosis refers to detection of cancers that would never have caused symptoms or death during a person’s lifetime; treating these cancers exposes people to harms without extending life.

The ACP’s recommendation for biennial screening rests on balancing modest gains in early detection from annual screening against the substantially higher rate of false positives, extra procedures and health‑system costs.

For older adults the calculus includes competing risks from other illnesses and shorter remaining life expectancy, which can reduce the potential benefit of detecting slow‑growing cancers.

How strong the evidence is

Evidence comes primarily from large population studies, randomised trials and systematic reviews of human screening data across the globe. These data are robust for comparing broad strategies in average‑risk populations, especially for women aged 50–74.

Limitations include:

• Many randomised trials were conducted decades ago, before widespread use of modern imaging technology, which may affect applicability today.
• Observational studies of contemporary practice can show associations but are more prone to bias.
• Data on subgroups, such as women with very dense breasts or particular genetic risks, are less complete.
• Long‑term outcomes for different screening intervals with modern DBT technology are still emerging.

Because of these limitations, the ACP frames some recommendations (notably for women 40–49 and for those with dense breasts) as decisions that should be personalised rather than blanket rules.

What this means for patients and the public

For women aged 50–74 at average risk, the new guidance supports having a screening mammogram every two years.

For those aged 40–49, the guidance stresses shared decision‑making, women should discuss their personal risk factors, values about potential benefits and harms, and preferences with their clinician before choosing annual screening, biennial screening, or no routine screening.

Women aged 75 or with limited life expectancy should talk with their clinician about whether continued screening is likely to be helpful.

Women with a strong personal or family history of breast cancer, known high‑risk genetic variants such as BRCA1/2, previous high‑dose chest radiation, or other risk factors should follow specialised screening pathways; the ACP guidance applies to average‑risk individuals.

Always talk to your healthcare providers for medical advice.

Treatments, prevention and screening options

Screening is only one part of breast cancer control. Preventive measures include risk‑reducing strategies for women at high risk, such as enhanced surveillance, chemoprevention or risk‑reducing surgery in selected cases, guided by specialist assessment.

DBT is increasingly available and may be preferred where accessible, particularly for women with dense breasts, because it can improve detection and reduce recalls. Supplemental MRI or ultrasound is generally reserved for higher‑risk individuals, not average‑risk women with dense tissue, according to the ACP statement.

What experts disagree about

Some radiology and oncology groups have criticised the ACP guidance, arguing it relies on older data and risks delayed diagnosis in women aged 40–49 and in women with dense breasts. They emphasise that modern annual screening and more sensitive imaging can find cancers earlier and save lives.

The ACP and its critics broadly agree that screening decisions involve trade‑offs between earlier detection and the harms of false positives and overdiagnosis, but they weigh those trade‑offs differently.

These differences reflect varying interpretations of the evidence and different priorities for minimising harms versus maximising early detection.

What remains unknown and what comes next

Key unanswered questions include how modern imaging technologies and screening strategies perform over the long term, especially in younger women and those with dense breasts.

Ongoing and future research will compare outcomes from DBT versus 2D mammography, different screening intervals with contemporary imaging, and tailored screening based on individual risk models.

Better tools to stratify risk could allow more personalised screening that maximises benefits and minimises harms.

Conclusion

The ACP’s guidance aims to clarify screening for the average‑risk population by privileging a balance between benefit and harm and by promoting shared decision‑making.

It does not eliminate screening options; rather, it encourages conversations between women and clinicians about personal risk and preferences.

For anyone unsure about what is best for them, the practical next step is to discuss individual risk factors, family history and the pros and cons of different screening schedules with a primary care clinician or breast specialist.