MUGA Scans and Anthracyclines Cancer Diagnostic Tests

Nuclear Medicine Tests Heart Muscle Before Chemotherapy

Heart Anatomy
Heart Anatomy. Illustration © A.D.A.M.

Before I could be treated with an anthracycline (a powerful chemotherapy drug) in 2002, I had to have a special test done on my heart -- a test called a multiple uptake gated acquisition scan, or MUGA scan for short.

The need for the test took me a bit by surprise, but given the fact that one type of anthracycline -- Adriamycin -- has been nicknamed "The Red Devil" by some, perhaps I shouldn't have been.

This thick, ruby-red liquid is given along with other drugs for the treatment of early-stage breast cancer. While tough on cancer cells (good), it can also be tough on your heart muscle (not good at all).

Drugs in the anthracycline class are made from the Streptomyces bacteria. These drugs are terrifically powerful antibiotics, but are too toxic to be used for ordinary infections. Anthracyclines are used to treat more kinds of cancer than any other class of chemotherapy drugs. Other examples of anthracyclines include Daunorubicin (Daunomycin) and Epirubicin.

In order to understand more about anthracyclines and MUGA scans, I looked up what the experts say on UpToDate -- a trusted electronic reference that is used by many of the oncologists who treat breast cancer patients.

If you are in the same boat as I was, a bit confused about the powerful drug you're being given and the test you never thought you'd need, read this excerpt and the takeaways that will help you get a better handle on anthracyclines and your heart.

Myocardial Function Assessment: A Discussion on Diagnosis and Staging Workup From UpToDate

"Many women with early stage breast cancer will be recommended adjuvant anthracycline-containing chemotherapy. Anthracyclines such as doxorubicin are associated with a dose-limiting, cumulative cardiotoxicity. Although the dose received in most adjuvant regimens (240 mg/m2 of doxorubicin) is lower than that which significantly increases the risk for cardiotoxicity (≥450 mg/m2), routine pretreatment assessment of left ventricular function with multiple gated acquisition (MUGA) scans is a common practice. Women with LVEFs lower than 30 to 35 percent should not receive doxorubicin."

 

Breaking Down the Basics

How Do Anthracyclines Affect My Heart?

Anthracyclines are cardiotoxic, meaning they are potentially damaging to the heart muscle. If your heart muscle is damaged by an anthracycline, you may be at risk for heart failure, a problem that may not show up until years after your treatments have ended. Because of this potential damage to your heart, there is a limit to how much can be given overall. Your doctor should calculate your cumulative dose, so that treatment can be stopped before the maximum amount is reached.

What Exactly Is a MUGA Scan and an LVEF?

A MUGA scan is a test that takes images of your heart as it pumps. It is used for many reasons; for patients who will need chemotherapy, it is done to see how well your heart pumps blood. The result it produces is called your ejection fraction. Specifically, this test lets your doctor see how much blood your left ventricle pumps every time your heart beats. That result is known as your left ventricular ejection fraction (LVEF).

Who Should Not Be Treated With Anthracyclines?

If you have an existing heart condition, you might not be a good candidate for anthracycline chemotherapy. After a MUGA scan, if your LVEF score is already low, your doctor may not want to risk damaging your heart further.

Should You Have a MUGA Scan?

Patients who are candidates for treatment with Herceptin (trastuzumab) may wonder if they should get a MUGA scan, since cardiotoxicity is a potential complication if anthracyclines and Herceptin are given together. However, because of this potential, these drugs are not given in combination. That being said, the drugs can be given sequentially; although a high rate of cardiotoxicity remains, good monitoring -- via MUGA scans -- can help reduce related problems before they get serious.

If trastuzumab is in your future, a minimum of one MUGA scan -- conducted before you start your drug treatment -- is recommended. Additional MUGA scans during therapy and for a short time after trastuzumab treatment is completed are also routinely done.

Note: Some centers rely on an echocardiogram instead of a MUGA scan.

Want to learn more? See UpToDate’s topic, "Diagnostic evaluation and initial staging workup of women with suspected breast cancer: Myocardial Function Assessment," for additional in-depth, current and unbiased medical information on breast cancer, including expert physician recommendations.

Source:

Laura J Esserman, and Bonnie N Joe, "Diagnostic evaluation and initial staging workup of women with suspected breast cancer: Myocardial Function Assessment" UpToDate. Accessed: January 2009.

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