# Prospective Multimodal Assessment of Radiation-Induced Subclinical Cardiac Changes in Patients with Left Breast Cancer Using Hematologic Biomarkers, Echocardiography, and 18F-FDG PET/CT: A Pilot Study

## TL;DR

This study investigates early heart changes in left breast cancer patients after radiation therapy using blood tests, heart imaging, and PET scans.

## Contribution

The study is the first to use a multimodal approach to detect subclinical cardiac changes in left-sided breast cancer patients after radiation therapy.

## Key findings

- Transient changes in cardiac biomarkers were observed but returned to normal after months.
- Persistent metabolic changes in irradiated heart regions were detected up to one year post-treatment.
- Subtle strain abnormalities were found despite normal heart function and no symptoms.

## Abstract

Radiation therapy after breast-conserving surgery is an essential treatment for breast cancer, but in left-sided disease the heart may be exposed to radiation, raising concerns about cardiac toxicity. Although clinically apparent heart disease usually develops years after treatment, subtle myocardial changes may occur much earlier without symptoms. In this prospective pilot study, we evaluated early subclinical cardiac changes in patients with left-sided breast cancer treated with postoperative radiation therapy without chemotherapy. Using blood biomarkers, echocardiography, and 18F-FDG PET/CT, we assessed inflammatory, functional, and metabolic myocardial changes over one year. We observed transient alterations in cardiac biomarkers, persistent metabolic changes in irradiated myocardial regions, and subtle strain abnormalities despite preserved cardiac function and absence of clinical symptoms. These findings suggest that microscopic radiation-induced myocardial changes can persist for at least one year and highlight the importance of early cardiac monitoring and strategies to reduce cardiac radiation exposure in breast cancer radiation therapy.

Background/Objectives: This prospective study aimed to investigate asymptomatic microscopic changes in the myocardium following postoperative radiation therapy (RT) in patients with left breast cancer using multi-medical assessment techniques. Methods: This study included 16 left-sided breast cancer patients who received postoperative RT between January 2021 and December 2022 at our institution. Cardiac examinations were performed before RT and at 1, 12, 24, and 48 weeks after RT. We conducted comparative analyses between pre-RT and various post-RT time points, exploring correlations between changes in hematologic biomarkers, global longitudinal strain (GLS), and myocardial metabolism. Results: Inflammatory biomarkers such as the neutrophil–lymphocyte, platelet–lymphocyte, and lymphocyte–monocyte ratios changed between the pre- and post-RT periods but returned to normal levels after several months. However, troponin T and soluble suppression of tumorigenicity 2 showed sustained changes during the 1-year follow-up period. Among echocardiographic parameters, GLS_LAX showed a significant difference between pre-RT and post-RT assessments. Additionally, irradiated and non-irradiated myocardial metabolic ratios on 18F-fluorodeoxyglucose positron emission tomography/computed tomography differed between pre-RT and post-RT and remained altered up to one year after treatment. Conclusions: These findings suggest that subclinical myocardial changes may persist following RT, although the clinical significance of subclinical myocardial changes remains uncertain and warrants further investigation.