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Cancer Atlas 2026 · Breast cancer
Breast Cancer Biomarkers and Early Detection in 2026: Screening, Tissue Markers and Blood Tests
Breast cancer is the most commonly diagnosed cancer in women worldwide, and most cases found early are survivable. This Atlas chapter explains how it is found today, which biomarkers guide treatment, and what blood tests can and cannot do. It separates established practice from research, using sources dated to 1 October 2026.
At a glance
Global burden, 2024
About 2.43 million new cases and 694,000 deaths (GLOBOCAN 2024)
US 5-year survival
91.9% overall: 100.0% localized, 33.8% distant (SEER, 2016–2022)
Screening
Mammography. USPSTF: every 2 years from age 40 to 74. No blood test is recommended for screening
Key biomarkers
ER, PR and HER2 on tissue; BRCA1/2, PIK3CA and ESR1 for drug selection
OncoFirm™ status
Assays in development; research use only; no breast cancer test or claim
On this page
Key numbers
Breast cancer in three numbers
2.43 Mnew breast cancer cases worldwide in 2024
100%5-year relative survival at localized stage (US)
33.8%5-year relative survival at distant stage (US)
Sources: GLOBOCAN 2024 (IARC) and SEER Cancer Stat Facts (cases diagnosed 2016–2022).
Burden
How common is breast cancer?
Breast cancer is the second most commonly diagnosed cancer in the world. In women it is the leading cancer for both new cases and deaths. The GLOBOCAN 2024 estimates count 2,434,087 new cases in 2024 (11.8% of all cancers) and 693,660 deaths. This chapter is part of the OncoFirm™ Cancer Atlas 2026.
In the United States, the American Cancer Society (ACS) estimates 321,910 new invasive breast cancers in women in 2026. It also expects 60,730 cases of ductal carcinoma in situ (DCIS), 2,670 cases in men and 42,140 deaths in women. Incidence rose about 1% per year from 2013 to 2022, and faster in women under 50 (1.4% per year). The death rate fell 44% from its 1989 peak through 2023.
Outcomes are uneven. A crude ratio of same-year deaths to new cases is about 0.29 worldwide and about 0.13 in the US. This is not a survival statistic, but it shows how much stage at diagnosis and access to diagnosis and treatment matter. Inside the US, 5-year relative survival is 94% in White women and 84% in Black women (diagnoses 2015–2021).
Why stage matters
Survival depends on stage at diagnosis
Five-year relative survival by stage at diagnosis for female breast cancer, with the share of cases found at each stage. US cases diagnosed 2016–2022. Source: SEER Cancer Stat Facts: Female Breast Cancer (National Cancer Institute).
The chart uses US SEER registry data for cases diagnosed from 2016 to 2022. Relative survival compares people who have a cancer with the general population. Five-year relative survival is 91.9% for all stages combined. It is 100.0% for localized disease, 87.5% for regional disease and 33.8% for distant disease (cancer that has spread to other organs).
A figure of 100.0% does not mean that no one dies. It means that, over five years, survival cannot be told apart statistically from that of women without breast cancer. About 64% of cases are found while localized, 27% at regional stage and 6% at distant stage. Compare this with ovarian cancer, where 54% of cases are already distant. See why early detection matters.
Screening
Screening today: mammography, on two US schedules
Imaging is the only guideline-endorsed way to find breast cancer early. US guidance is not fully aligned (status as of 1 October 2026).
- USPSTF (30 April 2024): mammography every 2 years for women aged 40 to 74 (Grade B). Evidence is rated insufficient for screening at 75 and older, and for extra ultrasound or MRI in women with dense breasts.
- ACS (based on its 2015 guideline): optional yearly mammography at 40 to 44, yearly at 45 to 54, then every 2 years or yearly from 55. Women at high risk, such as known BRCA1/2 carriers, are advised to have MRI plus a mammogram every year, typically from age 30.
- Dense breasts: since 10 September 2024, an FDA rule requires every US mammography report to state breast density.
The strongest new evidence concerns artificial intelligence (AI). The Swedish MASAI trial randomized about 106,000 women to AI-supported reading or standard reading by two radiologists. Full results appeared in The Lancet in early 2026. Interval cancers (cancers diagnosed between screening rounds) were 1.55 per 1,000 women with AI and 1.76 per 1,000 without, 12% lower. Sensitivity was 80.5% versus 73.8%. Specificity was 98.5% in both arms. Earlier MASAI reports showed 44% fewer screen readings by radiologists. The authors state that the study does not support replacing health professionals with AI.
No blood test screens for breast cancer. No serum protein marker has a screening role. One multi-cancer blood test reported 30.5% sensitivity for breast cancer across all stages in a case-control study, so it cannot replace mammography.
Biomarkers
Established biomarkers by role
A biomarker is a measurable sign of disease or of likely response to treatment. In breast cancer, the markers that drive care are measured on tumor tissue or tumor DNA, not on serum proteins. Roles are defined in Cancer biomarkers explained.
| Biomarker | Type | Used for | Not used for |
|---|---|---|---|
| ER and PR (tissue) | Classifying, predictive | Defining subtype; selecting endocrine therapy | Screening |
| HER2 (tissue) | Classifying, predictive | Selecting HER2-targeted drugs, including for HER2-low and HER2-ultralow disease | Screening |
| Gene-expression assays (Oncotype DX, MammaPrint and others) | Prognostic | Chemotherapy and endocrine decisions in early ER-positive, HER2-negative disease | Diagnosis |
| Germline BRCA1/2 (blood) | Predictive; inherited risk | Olaparib or talazoparib eligibility; identifying women who need yearly MRI | Detecting a cancer |
| PIK3CA, AKT1, PTEN (tissue or plasma) | Predictive | Selecting alpelisib or capivasertib with endocrine therapy | Early detection |
| ESR1 mutations (plasma ctDNA) | Predictive | Selecting newer oral ER-targeted drugs in metastatic disease | Screening; recurrence surveillance |
| PD-L1 (tissue) | Predictive | Pembrolizumab plus chemotherapy eligibility in metastatic disease | Screening |
| CEA, CA 15-3, CA 27.29 (serum) | Monitoring adjunct | Adjunct only when monitoring metastatic disease | Screening, diagnosis, or follow-up of people without symptoms |
HER2-low and HER2-ultralow are newer treatment categories read from the same tissue stain, immunohistochemistry (IHC). HER2-low means IHC 1+, or IHC 2+ with a negative gene test. HER2-ultralow means IHC 0 with some membrane staining. On 27 January 2025 the FDA approved trastuzumab deruxtecan for hormone receptor-positive, HER2-low or HER2-ultralow metastatic breast cancer after endocrine therapy. A companion diagnostic, a test required to select patients for a drug, followed on 30 January 2025.
ESR1 is the first breast cancer marker for which blood is the preferred sample. ESR1 mutations can emerge during endocrine therapy. A 2023 ASCO update says testing should be routine at recurrence or progression of ER-positive, HER2-negative metastatic disease. It prefers circulating tumor DNA (ctDNA, tumor DNA fragments in blood) over tissue.
Serum markers and antigens
Serum markers and tumor-associated antigens: established versus research
Established, with narrow use. MUC1 is a mucin, a heavily sugar-coated protein, that breast tumors shed into blood. CA 15-3 and CA 27.29 are serum assays for MUC1. CEA is a third serum marker. An ASCO guideline update of 16 July 2026 says all three remain discouraged for people without symptoms after primary treatment. The panel found no evidence that they detect recurrence earlier or improve survival, and they cause false positives. In metastatic disease, ASCO says they may serve as adjunctive assessments only.
Research stage. Tumor MUC1 often carries shortened sugar chains called glycans: the Thomsen-Friedenreich antigen (TF, also called CD176), Tn and sialyl-Tn. These are covered in Tumor-associated antigens and in our guide to the TF antigen. In one study of 226 primary breast cancers, TF staining correlated with lymph-node spread and predicted worse survival in some groups, including triple-negative disease. A 2010 review reported Tn in almost 90% of breast cancers. It reported sialyl-Tn in at least 25% to 30%, with estimates from 20% to 80% depending on the detection method.
Limits. These are tissue studies, mostly from single centers, and results change with the antibody or lectin used. No TF, Tn or sialyl-Tn test is FDA cleared or guideline endorsed for breast cancer, and we found no validated serum assay. The largest vaccine trial aimed at sialyl-Tn (1,028 women with metastatic breast cancer) showed no benefit in time to progression or survival.
Emerging
Emerging approaches in 2025–2026
Liquid biopsy has earned its place in breast cancer for choosing treatment in metastatic disease, not for detection. The clearest shift is ESR1 testing in blood as a companion diagnostic for new oral endocrine drugs:
- Imlunestrant: FDA approved in September 2025 for ESR1-mutated advanced breast cancer after endocrine therapy, with a plasma ctDNA companion diagnostic.
- Vepdegestrant: FDA approved on 1 May 2026. In the VERITAC-2 trial behind the approval, median progression-free survival was 5.0 months versus 2.1 months with fulvestrant.
- Camizestrant: FDA accelerated approval on 4 September 2026. In SERENA-6, patients switched drug when a blood test found an ESR1 mutation, before scans showed progression. Median progression-free survival was 16.0 versus 9.2 months. Whether early switching improves overall survival is unresolved.
ctDNA for recurrence surveillance is not established. This use is called molecular residual disease (MRD) testing. ASCO’s July 2026 update says ctDNA cannot be recommended for recurrence monitoring outside a clinical trial. Data at ESMO Breast Cancer 2026 show why. In the TRAK-ER study, ctDNA was detected in 11.6% of patients, and 42.9% of them already had recurrent disease at first detection. Across the trials reported, 27% to 72% of ctDNA-positive patients already had metastases. No trial has shown that acting on the result helps.
Multi-cancer early detection (MCED). No MCED test is FDA approved as of 1 October 2026. An FDA advisory panel backed the Galleri test on 23 September 2026, and the decision is pending. The randomized NHS-Galleri trial (142,942 adults) missed its primary endpoint, and breast cancer was not among its 12 prespecified cancers. See Emerging cancer diagnostic technologies and Multi-biomarker analysis.
Open questions
Open research questions
- Does changing therapy when ESR1 mutations appear in blood improve overall survival, or only delay progression?
- Can MRD tests find relapse early enough to change outcomes? Current tumor-informed tests need tissue, and assay design failed in 16.1% of TRAK-ER patients.
- What is the right extra test for dense breasts, and should screening continue after 75? USPSTF lists both as research needs.
- Do AI results from European double-reading programs carry over to other screening systems?
- Why does the US survival gap persist (94% versus 84%), and why is incidence rising fastest under age 50?
- Can glycan antigens such as TF, Tn and sialyl-Tn be turned into quantitative assays that add to imaging? This is a research hypothesis, not an established use.
OncoFirm™ roadmap
Where OncoFirm™ fits, and where it does not
OncoFirm™ is developing quantitative fluorescent lateral flow assays with a digital reader. They are in development, not cleared or approved by the FDA or any other regulatory authority, for research use only and not for sale. OncoFirm™ has no breast cancer assay and makes no screening claim.
CEA, in context
The CEA assay in development has a designed range of 1–100 ng/mL, with planned traceability to WHO standard 73/601. In breast cancer, guidelines treat CEA as an adjunct in metastatic monitoring only.
Quantitative platform
The fluorescent lateral flow platform aims for a numeric result in 20 minutes or less. That is a development target, not validated performance.
TF antigen concepts
Assay concepts for the TF antigen, which use peanut agglutinin as a binding lectin, are concept-stage. No TF-based test is validated for breast cancer.
Research collaboration
Research studies need clinical partners and honest endpoints. See clinical collaborations.
OncoFirm™ assays, reader and software are in development, have not been cleared or approved by the FDA or any other regulatory authority, are for research use only and are not for sale. Designed ranges and result times are development targets, not validated performance claims.
FAQ
Frequently asked questions
Is there a blood test that screens for breast cancer?
No. As of 1 October 2026, no blood test is recommended for breast cancer screening. Mammography is the guideline-endorsed method. One multi-cancer blood test reported 30.5% sensitivity for breast cancer in a case-control study, too low to replace imaging.
What are the main breast cancer biomarkers?
The estrogen receptor (ER), progesterone receptor (PR) and HER2 are measured on tumor tissue and define the subtype and treatment. Gene-expression assays inform chemotherapy decisions in early disease. BRCA1/2, PIK3CA and ESR1 testing select targeted drugs.
Should CA 15-3 or CEA be checked after breast cancer treatment?
Not in people without symptoms. A July 2026 ASCO guideline update says CEA, CA 15-3 and CA 27.29 remain discouraged for routine follow-up. They have not been shown to detect recurrence earlier or improve survival, and they cause false positives.
What does HER2-low mean?
HER2-low describes tumors with a small amount of HER2 on tissue staining: IHC 1+, or IHC 2+ with a negative gene test. Since January 2025, HER2-low and HER2-ultralow status can make some patients with hormone receptor-positive metastatic breast cancer eligible for trastuzumab deruxtecan.
Does OncoFirm™ offer a breast cancer test?
No. OncoFirm™ assays, reader and software are in development, are not cleared or approved by the FDA or any other regulatory authority, are for research use only and are not for sale. OncoFirm™ makes no breast cancer screening or diagnostic claim.
Cancer Atlas 2026
More in the Atlas
Related OncoFirm™ guides
Sources
References
- International Agency for Research on Cancer. Global Cancer Observatory: World fact sheet, GLOBOCAN 2024. gco.iarc.who.int/media/globocan/factsheets/populations/900-world-fact-sheet.pdf
- Sung et al. Global cancer statistics 2024: GLOBOCAN estimates of incidence and mortality worldwide for 34 cancers in 186 countries. CA: A Cancer Journal for Clinicians. 2026. DOI 10.3322/caac.70090. acsjournals.onlinelibrary.wiley.com/doi/10.3322/caac.70090
- American Cancer Society. Cancer Facts & Figures 2026. www.cancer.org/content/dam/cancer-org/research/cancer-facts-and-statistics/annual-cancer-facts-and-figures/2026/2026-cancer-facts-and-figures.pdf
- National Cancer Institute. SEER Cancer Stat Facts: Female Breast Cancer (read 1 October 2026). seer.cancer.gov/statfacts/html/breast.html
- US Preventive Services Task Force. Breast Cancer: Screening. Final recommendation statement, 30 April 2024. www.uspreventiveservicestaskforce.org/uspstf/recommendation/breast-cancer-screening
- American Cancer Society. Recommendations for the Early Detection of Breast Cancer (read 1 October 2026). www.cancer.org/cancer/types/breast-cancer/screening-tests-and-early-detection/american-cancer-society-recommendations-for-the-early-detection-of-breast-cancer.html
- US Food and Drug Administration. Final rule to amend the Mammography Quality Standards Act (MQSA) regulations. www.fda.gov/radiation-emitting-products/mammography-quality-standards-act-mqsa-and-mqsa-program/important-information-final-rule-amend-mammography-quality-standards-act-mqsa
- The ASCO Post. Randomized trial shows AI-supported mammography improves sensitivity and lowers interval cancer rate (MASAI trial, The Lancet). February 2026. ascopost.com/news/february-2026/randomized-trial-shows-ai-supported-mammography-improves-sensitivity-and-lowers-interval-cancer-rate/
- US Food and Drug Administration. List of Cleared or Approved Companion Diagnostic Devices (In Vitro and Imaging Tools). www.fda.gov/medical-devices/in-vitro-diagnostics/list-cleared-or-approved-companion-diagnostic-devices-in-vitro-and-imaging-tools
- OncLive. FDA approves companion diagnostic for T-DXd in HER2-ultralow metastatic breast cancer. January 2025. www.onclive.com/view/fda-approves-companion-diagnostic-for-t-dxd-in-her2-ultralow-metastatic-breast-cancer
- Henry et al. Biomarkers for systemic therapy in metastatic breast cancer: ASCO guideline update (summary). Journal of Clinical Oncology. 2022. DOI 10.1200/JCO.22.01063. www.guidelinecentral.com/guideline/1890548/
- The ASCO Post. Guideline update on ESR1 mutation testing in ER-positive, HER2-negative metastatic breast cancer (Burstein et al., Journal of Clinical Oncology, 2023). 25 June 2023. ascopost.com/issues/june-25-2023/guideline-update-provides-new-testing-and-treatment-recommendations-for-patients-with-er-positive-her2-negative-metastatic-breast-cancer-with-esr1-mutations/
- Andre et al. Biomarkers for adjuvant endocrine and chemotherapy in early-stage breast cancer: ASCO guideline update. Journal of Clinical Oncology. 2022. DOI 10.1200/JCO.22.00069. ascopubs.org/doi/10.1200/JCO.22.00069
- CancerNetwork. Top 9 takeaways from ASCO's 2026 breast cancer surveillance update (ASCO guideline update, Journal of Clinical Oncology, 16 July 2026). www.cancernetwork.com/view/top-9-takeaways-from-asco-s-2026-breast-cancer-surveillance-update
- Study of Thomsen-Friedenreich antigen staining and prognosis in 226 primary breast cancers. Breast Cancer Research and Treatment. 2020. DOI 10.1007/s10549-019-05503-6. link.springer.com/article/10.1007/s10549-019-05503-6
- Cazet et al. Review of tumor-associated carbohydrate antigens in breast cancer. Breast Cancer Research. 2010;12:204. link.springer.com/article/10.1186/bcr2577
- Miles et al. Phase III trial of the sialyl-Tn vaccine STn-KLH in women with metastatic breast cancer. The Oncologist. 2011;16(8):1092–1100. academic.oup.com/oncolo/article/16/8/1092/6401188
- Guardant Health. FDA approves Guardant360 CDx as companion diagnostic for imlunestrant in ESR1-mutated advanced breast cancer. Press release, 29 September 2025. investors.guardanthealth.com/press-releases/press-releases/2025/FDA-Approves-Guardant360-CDx-as-Companion-Diagnostic-for-Eli-Lilly-and-Companys-Inluriyo-imlunestrant-for-Treatment-of-ESR1-mutated-Advanced-Breast-Cancer/default.aspx
- OncLive. FDA approves companion diagnostic for vepdegestrant in ESR1-mutated, ER-positive, HER2-negative advanced breast cancer. May 2026. www.onclive.com/view/fda-approves-companion-diagnostic-for-vepdegestrant-in-esr1-er-her2-negative-advanced-breast-cancer
- The ASCO Post. FDA approves camizestrant combination regimen for locally advanced or metastatic breast cancer. September 2026. ascopost.com/news/september-2026/fda-approves-camizestrant-combination-regimen-for-locally-advanced-or-metastatic-breast-cancer/
- ESMO Daily Reporter. The role of ctDNA surveillance is still uncertain in early breast cancer. ESMO Breast Cancer 2026, May 2026. dailyreporter.esmo.org/esmo-breast-cancer-2026/latest-news/the-role-of-ctdna-surveillance-is-still-uncertain-in-early-breast-cancer
- GRAIL. Galleri test performance (page for health care professionals; company source). www.galleri.com/hcp/galleri-test-performance
- The ASCO Post. Annual Galleri screening reduced stage IV cancer diagnoses but missed primary endpoint in first randomized MCED trial. June 2026. ascopost.com/news/june-2026/annual-galleri-screening-reduced-stage-iv-cancer-diagnoses-but-missed-primary-endpoint-in-first-randomized-mced-trial/
- Targeted Oncology. FDA advisory panel review of the Galleri multi-cancer early detection test. September 2026. www.targetedonc.com/view/fda-panel-galleri-multi-cancer-early-detection-test
About this article. Figures come from GLOBOCAN 2024, the American Cancer Society, SEER, USPSTF, ASCO guideline summaries and FDA notices; several trial results are taken from conference or trade reports and may change on full publication. Part of the OncoFirm™ Cancer Atlas 2026, written by the OncoFirm™ Scientific Team from the sources linked above and reflecting public information as of 1 October 2026. It is for education and is not medical advice. OncoFirm™ has no affiliation with the companies or tests named. OncoFirm™ assays are in development, have not been cleared or approved by the FDA and are not available for sale.
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