Quick Facts
- Sample: Blood (serum)
- Fasting: No fasting required
- Turn-around: 4-6 business days. May take longer based on weather, holiday, or lab delays.
Benefits
- Monitor treatment response - Track how well your breast cancer therapy is working
- Detect recurrence early - Identify cancer return 5-13 months before symptoms appear
- Convenient testing - No physician referral needed for proactive health monitoring
- Quick results - Get answers within 1-2 business days for timely decisions
- Cost-effective - Affordable monitoring between regular medical appointments
- Professional support - Expert interpretation available through secure platforms
Who Is This Test For?
- Breast cancer patients undergoing active treatment for stages II-IV disease
- Cancer survivors monitoring for potential recurrence during follow-up care
- Metastatic patients tracking disease progression and treatment effectiveness
- High-risk individuals with strong family history seeking proactive surveillance
- Anyone with symptoms suggesting possible breast cancer recurrence
How It Works – Just 3 Steps
- Order online — Purchase directly without doctor referral and schedule lab appointment
- Visit lab — Quick blood draw at certified laboratory near you
- Get results — Access confidential results online within few business days
FAQ
What does CA 15-3 measure? CA 15-3 measures a protein released by breast cancer cells into your bloodstream, helping monitor disease activity.
Can this test diagnose breast cancer? No, CA 15-3 is not used for diagnosis or screening—it monitors existing cancer and detects recurrence.
What's considered a normal result? Normal CA 15-3 levels are typically 30 U/mL or below, though ranges may vary by laboratory.
How often should I test? During treatment: every 1-3 months. During surveillance: every 3-6 months, or as recommended by your doctor.
Can other conditions raise CA 15-3? Yes, liver disease, infections, and benign breast conditions can sometimes elevate CA 15-3 levels.
Do I need to fast for this test? No fasting is required—you can eat normally before your blood draw.
More Details
What is the purpose of this test?
The CA 15-3 test measures a tumor marker protein produced by breast cells and released into the bloodstream (Mayo Clinic 2024). This protein, an epitope of the MUC1 glycoprotein, becomes overexpressed in cancerous breast tumors. The test serves as a valuable monitoring tool for advanced breast cancer patients during treatment and follow-up care, helping track treatment response and detect recurrence before symptoms appear.
While CA 15-3 demonstrates excellent specificity for breast malignancy at 91%, it's not suitable for cancer screening or early diagnosis (PMC Clinical Research 2021). Instead, it provides crucial information about disease progression and treatment effectiveness in patients with established breast cancer.
Who would benefit from this test?
This test is particularly valuable for breast cancer patients with Stage II-IV disease undergoing treatment, survivors monitoring for recurrence, and individuals with metastatic breast cancer tracking therapy response (Johns Hopkins 2025).
Health-conscious consumers utilizing direct-to-consumer lab services can benefit from proactive health monitoring capabilities, especially breast cancer survivors and high-risk individuals. The test offers convenient access to important tumor marker information without requiring physician referrals, enabling patients to track their health status between medical appointments.
When should I order a Cancer Antigen (CA) 15-3 Blood Test?
Consider ordering this test during active breast cancer treatment (every 1-3 months), post-treatment surveillance visits, or when experiencing symptoms suggestive of recurrence in breast cancer survivors (Clinical Laboratory Medicine 2003).
The test is most beneficial for monitoring established disease rather than initial detection, as sensitivity increases dramatically with disease stage—from just 7% in Stage I to 67-75% in Stage IV disease (PMC Research 2021).
How do I interpret the results?
CA 15-3 ≤ 30 U/mL
- What it means: Normal range
- Typical action: Continue routine monitoring
CA 15-3 between 30–50 U/mL
- What it means: Slightly elevated
- Typical action: Consider benign causes, repeat testing
CA 15-3 > 50 U/mL
- What it means: Significantly elevated
- Typical action: Urgent follow-up with oncologist
Changes in CA 15-3 levels over time are more clinically significant than single values—serial monitoring provides the most valuable insights.
Disclaimer: Reference ranges may vary by laboratory. Listed ranges are general guidelines and may differ from those used by the performing lab. Always consult your healthcare provider for interpretation.
Pre-test preparation
No fasting is required for CA 15-3 testing—you can eat normally before your appointment (Apollo Hospitals). However, discontinue biotin supplements at least 72 hours before testing if taking more than 5 mg/day to prevent interference with results.
Inform your healthcare provider about current medications, though most pharmaceuticals don't interfere with the test. The blood draw can be performed at any time of day without dietary restrictions.
How often should I get tested?
- Active treatment: Every 1–3 months
- Post-treatment surveillance: Every 3–6 months
- Metastatic disease: Every 1–2 months
- Long-term survivors: Every 6–12 months
Why early detection matters
Early detection of breast cancer recurrence can significantly impact treatment outcomes and survival rates. CA 15-3 testing can detect recurrence 5-13 months before conventional methods, with 37% of breast cancer recurrences first identified by rising CA 15-3 levels before clinical symptoms appear (PMC Research Study 2021).
With breast cancer affecting 1 in 8 women and 310,720 new cases expected in 2024, proactive monitoring through tumor markers provides crucial early warning capabilities (American Cancer Society 2024). The 99% five-year survival rate when detected at localized stage emphasizes the importance of vigilant monitoring.
Related tests you may consider
CA 27.29 Tumor Marker measures a different epitope of the same MUC1 protein, potentially offering higher sensitivity in some patients. While generally concordant with CA 15-3, it should not be used interchangeably.
Carcinoembryonic Antigen (CEA) serves as a complementary tumor marker with higher sensitivity (75%) while CA 15-3 demonstrates higher specificity (97%). The combination provides enhanced diagnostic accuracy.
Breast Cancer Blood Test Panel – Measures CA 27.29, CA 15-3, and CEA tumor markers to help monitor the presence, progression, and treatment response of breast cancer. These markers may aid in evaluating metastatic disease and potential recurrence.
