Why the guidelines finally changed
The USPSTF published its updated breast cancer screening recommendation in April 2024. The headline: start mammograms at 40, not 50, every other year through age 74.
Two things drove this change. First, breast cancer incidence in younger women has been rising. The rate of invasive breast cancer in women aged 40–49 increased by about 2% per year between 2015 and 2019. Second, better data showed the net benefit of earlier screening is greater than previously modelled — catching more cancers in younger women who, when treated, have decades of life ahead of them.
The ACOG updated its guidelines independently in October 2024 to align: average-risk women should start mammogram screening at 40. The American Cancer Society maintains a slightly more nuanced position, offering that women in their 40s have the option to start annually — but neither major body now recommends waiting until 50.
The insurance angle matters: once the USPSTF recommends a preventive service, Medicare, Medicaid, and most commercial insurers are required to cover it without cost-sharing. Women aged 40–74 should be able to get screening mammograms at no out-of-pocket cost in the US.
Dense breasts: what this means for your screening
Dense breast tissue is normal. It refers to the ratio of fibrous and glandular tissue to fatty tissue in the breast. Around 40% of women have dense breasts, and it matters for two reasons: it increases breast cancer risk modestly, and it reduces mammogram sensitivity because dense tissue and tumours appear similarly on X-ray.
After your mammogram, you'll receive a report stating your breast density (A through D, least to most dense). If you're Category C or D, ask your doctor whether supplemental ultrasound or MRI screening is appropriate for you. In many US states, radiology centres are now legally required to inform you if you have dense breasts.
For women with dense breasts, ultrasound can catch cancers that mammography misses — but it also produces more false positives. Breast MRI is the most sensitive screening tool and is recommended for women at high lifetime risk (generally 20–25% or higher). This is a conversation worth having rather than assuming your standard mammogram is sufficient.
If you have a family history
Average-risk guidelines don't apply to everyone. If you have a first-degree relative (mother, sister, daughter) who had breast cancer, your own risk is roughly doubled. If that relative was diagnosed before 50, your risk is higher still.
Current guidelines suggest starting screening 10 years before the youngest age at which a close relative was diagnosed — so if your mother was diagnosed at 42, discuss starting at 32. You may also be a candidate for BRCA1/BRCA2 genetic testing, particularly if there is breast and ovarian cancer on the same side of the family. A referral to a genetic counsellor is the right next step — not a direct-to-consumer DNA test.
The USPSTF's 2024 update noted an additional driver: health equity. Black women are 40% more likely to die from breast cancer than white women, partly because of a higher incidence of aggressive subtypes and later diagnosis. Starting screening at 40 catches more of these cancers at earlier, treatable stages.
What to ask at your next appointment
If you're approaching or have passed 40 and haven't been referred for a mammogram, ask. You don't need to wait for the doctor to bring it up. Ask about your breast density result after each mammogram. If you have any family history of breast or ovarian cancer, tell your doctor specifically — it changes the screening plan.
References
- US Preventive Services Task Force. Breast Cancer: Screening Recommendation. April 30, 2024. USPSTF
- ACOG. Updates Recommendation on When to Begin Breast Cancer Screening Mammography. October 2024. ACOG
- American Cancer Society. Breast Cancer Screening Guidelines. ACS
- Sprague BL, et al. Prevalence of Mammographically Dense Breasts in the United States. Journal of the National Cancer Institute. 2014;106(10). PubMed