ESTRO 2024 - Abstract Book

S576

Clinical - Breast

ESTRO 2024

1 IRCCS San Matteo Polyclinic Foundation, Radiation Oncology, Pavia, Italy. 2 IRCCS San Matteo Polyclinic Foundation, Medical Physics, Pavia, Italy. 3 IRCCS San Matteo Polyclinic Foundation, Department of Surgery, Pavia, Italy. 4 IRCCS San Matteo Polyclinic Foundation, Department of plastic Surgery, Pavia, Italy. 5 IRCCS San Matteo Polyclinic Foundation, department of pathology, Pavia, Italy. 6 IRCCS San Matteo Polyclinic Foundation, Oncology, Pavia, Italy. 7 IRCCS San Matteo Polyclinic Foundation, Radiology, Pavia, Italy. 8 IRCCS San Matteo Polyclinic Foundation, department of surgery, Pavia, Italy

Purpose/Objective:

Cardiac toxicity following irradiation for left-sided breast cancer (LBC) is considered to be dose-dependent. We conducted a prospective analysis to investigate whether radiation therapy (RT) using the moderate deep inspiration breath hold (mDIBH) technique assisted by the Active Breathing Coordinator (ABC) could reduce the mean heart dose (MHD) and the mean/maximum doses to the left descending coronary artery (LAD). Furthermore, we analyzed the feasibility of this technique according different doses and treatment volumes.

Material/Methods:

We prospectively collected data from patients with LBC stages 0-III, who underwent RT using the ABC/mDIBH technique to assess its efficacy and benefits. Patients eligible for adjuvant RT to the breast or chest wall, capable of tolerating mDIBH, willing to undergo device training, and able to perform a 20-second breath hold were enrolled. Patients with poor hearing were excluded due to concerns about understanding breath hold instructions during RT. The primary endpoint was to compare ABC-assisted dosimetry with free-breathing plans, focusing on reducing MHD and mean/maximum LAD doses. Secondary endpoints included dose reduction to the heart and LAD, procedural success rate across different treatment schedules and target volumes, and adverse events.

Results:

A total of 207 patients with stages 0-III LBC were enrolled from November 2020 to July 2023. All patients underwent both free-breathing and ABC simulations. The primary endpoint was achieved, showing a significant reduction in MHD from 1.23 ± 0.64 Gy (free-breathing) to 0.90 ± 0.32 Gy (mDIBH) (p < 0.0143). Significant LAD sparing was also observed, with a decrease in Dmax from 20.63 ± 12.42 Gy (free-breathing) to 8.98 ± 5.10 Gy (mDIBH) (p < 0.0001) and a decrease in Dmean from 4.64 ± 4.55 Gy (free-breathing) to 2.29 ± 0.86 Gy (mDIBH) (p < 0.0073); these analysis were conducted on a homogeneous subgroup of patients characterized by a 40.05 Gy dose and left breast volume. Of the 207 patients, 195 received RT using ABC, resulting in a procedural success rate of 94%. The mean breath-hold volume was 1.1 L, and the mean breath-hold duration was 25 s. Three prescription doses were utilized: 40.05 Gy +/- SIB(65%) in 135 patients, 26 Gy(10%) in 21 patients, and 50 Gy +/- SIB(13%) in 39 patients. Of the 39 patients who received 50 Gy, 20 underwent breast reconstruction. The average cardiac dose in this subgroup was 1.347 Gy, indicating excellent dose sparing even for larger treatment volumes, such as the reconstructed chest wall and lymph nodes. No adverse events were reported, regardless of dose or volume.

Conclusion: