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Protecting Your Heart While Fighting Breast Cancer: What Every Woman Should Know This October

Medically Reviewed & Edited

Board-Certified Invasive Cardiologist
Encinitas and La Jolla, CA

Developed with digital research and writing assistance, then medically reviewed and edited by Dr. Rasch to ensure clinical accuracy and adherence to current evidence-based guidelines.

October is Breast Cancer Awareness Month, and while we focus on pink ribbons and early detection, there’s another conversation we need to have. If you or someone you love is facing breast cancer treatment, understanding how these therapies can affect your heart might be one of the most important discussions you’ll have with your medical team.

Why Your Cardiologist Cares About Your Cancer Treatment

I’ve spent years caring for hearts in San Diego, and increasingly, I’m sitting down with women who’ve beaten breast cancer but are now dealing with heart problems they never expected. The truth is, many of the same treatments that save lives from cancer can put stress on your heart. As a cardiologist, I want you to know about this connection before you start treatment, so we can protect both your life and your heart health.

When we talk about breast cancer treatment, we’re often discussing powerful medications like doxorubicin (an anthracycline chemotherapy) and trastuzumab (Herceptin), along with radiation therapy. These treatments work remarkably well against cancer cells. However, they can also affect the heart muscle in ways that may not show up right away.

The medical term is “cardiotoxicity,” but what does that really mean for you? Think of your heart as a muscle that needs to contract and relax millions of times each day. Some cancer treatments can weaken this muscle, making it less efficient at pumping blood throughout your body. This can happen during treatment or sometimes years later.

Anthracycline chemotherapy drugs carry a low but real risk of weakening the heart muscle (cardiomyopathy). The risk increases with higher cumulative doses. Trastuzumab, which targets HER2-positive breast cancers, can cause cardiac dysfunction, especially when given with or after anthracyclines. Radiation therapy to the left breast can affect nearby cardiac structures, potentially leading to coronary artery disease, valve problems, or pericardial complications down the road. Aromatase inhibitors, commonly used for hormone receptor-positive cancers, may increase your risk of heart disease and stroke. Newer medications like CDK 4/6 inhibitors can occasionally cause heart rhythm abnormalities.

Research shows that up to 16% of younger women (under 65) who receive anthracyclines or trastuzumab develop some form of cardiovascular disease within 10 years of treatment. That’s a significant number, and it’s why we need to be proactive.

What Happens to Your Heart During Treatment

Your heart is under stress during cancer therapy. While your ejection fraction (the percentage of blood your heart pumps out with each beat) might look normal on tests, subtle changes can be happening at the cellular level. This is where modern cardiology has made real advances.

We now have a technique called global longitudinal strain (GLS) imaging. Think of it as a more sensitive way to measure how well your heart muscle is contracting. Regular echocardiograms measure your ejection fraction, which is useful, but GLS can detect problems earlier, often before your ejection fraction drops. This early warning system allows us to intervene before permanent damage occurs.

When GLS drops by 12 to 15% from your baseline measurement during cancer treatment, even if your ejection fraction looks fine, we know your heart muscle is under strain. This is our signal to act.

The Monitoring Plan You Should Expect

If you’re starting treatment with anthracyclines, trastuzumab, or left-sided radiation, here’s what monitoring typically looks like:

Before you start treatment, you should have a baseline echocardiogram with GLS measurement. This gives us your personal starting point. If you’re receiving trastuzumab, expect repeat echocardiograms every three months during treatment. For anthracycline therapy, we typically check your heart function at the end of treatment and again six months later. If you’re getting high-dose anthracyclines (over 240 mg/m²), we monitor more frequently.

After treatment ends, annual check-ins are important, with imaging reserved for those who have symptoms or high-risk features. Late-onset heart problems can show up years later, so staying connected with your healthcare team matters.

Your oncologist and cardiologist should be working together on this. If you’re being treated for breast cancer and nobody has mentioned cardiac monitoring, bring it up. You deserve a coordinated care plan that addresses both your cancer and your heart.

When We Need to Protect Your Heart

Sometimes during treatment, your GLS will show that early warning sign we talked about. When this happens, we don’t just watch and wait. We start medications that protect your heart muscle.

Two classes of medications have proven effective: ACE inhibitors (like ramipril or enalapril) and beta-blockers (like bisoprolol or carvedilol). These medications actively protect your heart muscle from further injury while you continue cancer treatment.

The SUCCOUR-MRI trial showed something important. When doctors started heart-protective medications in women whose GLS had declined (even though their ejection fraction was still normal), those women had better heart function a year later compared to women who didn’t get early intervention. The key word here is “early.” We’re catching problems before they become permanent.

Research suggests bisoprolol may offer slightly better protection for GLS preservation compared to ramipril, though both medications help. I often consider your other health conditions when choosing which medication to start. If you have asthma, a beta-blocker might not be ideal. If you have certain kidney conditions, we might lean toward a beta-blocker instead of an ACE inhibitor.

Here’s something really important: these heart medications don’t interfere with your cancer treatment. They don’t make chemotherapy less effective or increase cancer recurrence. This was a concern early on, but multiple studies have confirmed that protecting your heart doesn’t compromise your cancer outcomes.

Risk Factors That Matter

Not everyone has the same risk of developing heart problems from cancer treatment. Certain factors increase your risk:

If several of these apply to you, having a consultation with a cardiologist before starting cancer treatment is wise. We can optimize your blood pressure, cholesterol, and blood sugar control before you begin, giving your heart the best possible foundation.

What You Can Do Right Now

You’re not powerless here. While you’re going through treatment, and after, there are concrete steps that help protect your heart:

Stay physically active within the limits your oncologist sets. Even light walking helps maintain cardiovascular fitness. Don’t smoke, and if you do, this is an excellent time to quit. Ask your oncology team about smoking cessation resources. Eat a heart-healthy diet rich in fruits, vegetables, whole grains, and lean proteins. Limit processed foods and excess salt. Manage your blood pressure and blood sugar if you have diabetes or pre-diabetes. Take any prescribed heart medications consistently. Keep your cholesterol in check. Watch for symptoms like unusual shortness of breath, persistent fatigue that’s different from chemo fatigue, swelling in your legs or feet, or chest discomfort. Report these to your doctor right away.

Weight gain is common during breast cancer treatment, particularly with certain hormonal therapies. This isn’t about appearance. Excess weight increases your cardiovascular risk. If you’re gaining weight, talk to your team about nutrition counseling and safe exercise programs.

Looking at Long-Term Heart Health

Finishing cancer treatment is a major milestone worth celebrating. You’ve been through so much. However, your heart still needs attention in the years ahead.

Some heart problems from cancer treatment don’t show up until 5, 10, or even 15 years later, especially if you received both anthracyclines and chest radiation. This delayed cardiotoxicity is why annual check-ups that include cardiovascular assessment are important for all breast cancer survivors.

If you received anthracyclines, trastuzumab, or left chest radiation, I recommend staying connected with a primary care provider who knows your treatment history. They should be checking your blood pressure, cholesterol, and blood sugar annually. If you develop new symptoms like shortness of breath with activities you used to do easily, leg swelling, or unusual fatigue, don’t dismiss them as just getting older. These could be signs your heart needs attention.

Some women benefit from periodic echocardiograms even without symptoms, particularly if they received high-dose anthracyclines or combination cardiotoxic therapies. This is a conversation worth having with your doctor about three to five years after treatment ends.

When Your Ejection Fraction Drops

Sometimes despite our best efforts at prevention, the heart’s pumping function decreases. If your ejection fraction falls below 53%, or drops more than 10 percentage points from your baseline, we diagnose cancer therapy-related cardiac dysfunction.

Many women respond well to heart failure medications. The same medications we use for prevention (ACE inhibitors and beta-blockers) are also treatments. Sometimes we add other medications like aldosterone antagonists or newer agents called SGLT2 inhibitors.

The sooner we catch and treat this, the better the outcome. I’ve had patients whose heart function improved significantly with medication, allowing them to live full, active lives. Some even saw their ejection fraction return to normal range.

If your heart function declines significantly during cancer treatment, your oncologist might need to modify your regimen. Perhaps switching medications, reducing doses, or temporarily pausing treatment. This is a team decision involving you, your oncologist, and your cardiologist. The goal is always to cure your cancer while preserving your quality of life.

Questions to Ask Your Oncology Team

When you meet with your oncologist, consider asking these questions:

Don’t worry about asking “too many” questions. This is your health, and understanding your treatment plan is your right. Any oncologist worth their salt welcomes these questions and should have clear answers.

Final Thoughts This Awareness Month

This October, as we raise awareness about breast cancer, I want you to also be aware of the connection between cancer treatment and heart health. This isn’t meant to scare you. It’s meant to empower you.

If you’re facing breast cancer treatment, know that with proper monitoring and early intervention when needed, most women get through treatment with their hearts intact. The advances in both oncology and cardiology mean we can cure more cancers while causing less collateral damage to the heart.

If you’re a breast cancer survivor, even if your treatment was years ago, mention your treatment history at every doctor visit. Don’t assume that because you feel fine, your heart is fine. Get your blood pressure checked. Know your cholesterol numbers. Stay active. These simple things make a real difference.

And if you’re supporting someone through breast cancer treatment, help them advocate for cardiac monitoring. Offer to go to appointments and ask questions. Help them watch for worrisome symptoms. Your support matters more than you know.

We’ve made remarkable progress in treating breast cancer. Survival rates continue to improve. Now we need to make sure survivors live long, healthy lives with strong hearts. That’s why this dual awareness matters so much. Cancer health and cardiac health both deserve our attention.