FDG PET May Help Flag Early Cardiotoxicity in Breast Cancer Patients

Monday, December 1, 2025

By Melissa Silverberg

Watanabe

Cancer therapy–related cardiac dysfunction is a serious consequence for some breast cancer patients, yet clinicians still lack dependable tools to identify the earliest signs of heart injury before lasting damage occurs. A study presented on Sunday suggests that serial evaluation of fluorodeoxyglucose (FDG) positron emission tomography (PET)—the same scan routinely used for cancer staging—may help identify chemotherapy-related myocardial damage before changes appear on echocardiography or MRI.

“There is no reliable tool for early detection of cardiotoxicity of chemotherapy,” said Masaki Watanabe, MD, from Tokyo Women’s Medical University. “We aimed to identify warning signs before functional decline occurs.”

Dr. Watanabe said the research team was inspired by observations from everyday practice.

Serial PET Analysis During Chemotherapy

Researchers reviewed 535 FDG PET examinations performed before and after chemotherapy in 108 breast cancer patients between 2014 and 2025. Because myocardial FDG uptake varies with blood glucose and insulin levels and differs widely across individuals, single time-point interpretation is difficult. To address this, the researchers compared serial scans within each patient and calculated a myocardial standard uptake ratio (M-SUR).

“M-SUR reduces individual variability and the influence of blood glucose levels,” Dr. Watanabe said. “Using the aorta helps normalize myocardial uptake by accounting for differences in blood glucose and insulin levels at each scan.”

Patients were grouped by chemotherapy regimen: anthracyclines, HER2 inhibitors, immune checkpoint inhibitors (ICIs) or other treatments. The team analyzed 309 paired pre-/post-treatment datasets.

Uptake Increased After Anthracycline and ICI Therapy

The study found that myocardial FDG uptake increased after anthracycline-based chemotherapy and after ICI therapy, while HER2-targeted therapy and other regimens showed no significant change.

“I think inflammation plays a role in increasing myocardial FDG uptake with both chemotherapy regimens,” Dr. Watanabe said of the anthracycline and ICI groups. For anthracyclines, he said, mitochondrial injury may also shift the myocardium from fatty-acid metabolism toward glucose metabolism.

HER2 inhibitors showed a different pattern. “Unlike anthracyclines, which cause irreversible cell damage, or ICIs, which can trigger severe inflammation, HER2 inhibitors mainly affect heart cell function without killing the cells,” he said. “As a result, the cardiac effects are usually mild and reversible.”

In the anthracycline group, patients with increased myocardial uptake were more likely to be older and often showed abnormalities on electrocardiography, including atrioventricular conduction disturbances, ST-T wave changes and atrial fibrillation.

A Potential Noninvasive Tool for Earlier Detection

Dr. Watanabe said the results show that serial FDG PET can reveal metabolic abnormalities at a preclinical stage, before structural or functional changes become visible on standard cardiac imaging.

“It is difficult to distinguish physiological myocardial uptake from cardiotoxicity,” he said.

He also cautioned that in patients with a high metastatic burden, an apparent rise in myocardial uptake may partly reflect a sink effect rather than true metabolic activation.

“But it is important to focus on serial data for each patient. Understanding the patterns of normal physiological uptake also helps in identifying pathological accumulation," Dr. Watanabe said. "The main message is that oncology FDG PET may serve as a practical, noninvasive tool for early cardiotoxicity monitoring without requiring additional imaging.”

Access the presentation, “Serial FDG PET Analysis for Detection of Cardiotoxicity of Breast Cancer Chemotherapy,” (S1-SSNMMI01-1) on demand at RSNA.org/MeetingCentral.

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The RSNA 2025 Daily Bulletin is the official publication of the 110th Scientific Assembly and Annual Meeting of the Radiological Society of North America. Published online Sunday, November 30 — Thursday, December 4.

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