ESTRO 2024 - Abstract Book

S657

Clinical - Breast

ESTRO 2024

radiotherapy using continuous positive airway pressure (CPAP). The CPAP technique is a gated breathing technique that passively and continuously increases lungs volume, minimizing diaphragm excursion [5].

Material/Methods:

12 patients were enrolled in the study from June to September 2023, with a diagnosis of early-stage left breast cancer and the following inclusion criteria: BCS or mastectomy followed by adjuvant radiotherapy, without indication for lymph node irradiation, aged 18-70 years (median age of 61, 47-70 yrs), without severe cardiac or pulmonary comorbidities.

The prescribed dose was 40.05 Gy delivered in 15 daily fractions [6], boost was allowed until reaching a dose of 48 Gy.

All patients underwent a pulmonary examination and pulmonary function testing prior to the treatment planning.

Two planning computed tomography (CT) scans were acquired for each patient: the first one was performed in free breathing (FB), the second one by using CPAP device (pressure 15mmHg) (CPAP).

For the first 10 patients enrolled in the study, the planning CT with CPAP device was performed using the 4D technique to verify the stability of lung volume during the different respiratory phases and consequently the reduction of respiratory excursion by the CPAP device.

Two 3D-CRT field-in-field (3D-CRT FIF) treatment plans were generated for each patient, one for each CT scan (FB and CPAP).

Dosimetric data, in terms of target coverage and OARs doses (lungs, contralateral breast, heart, cardiac substructures like right atrium, left atrium, right ventricle, left ventricle, lateral wall of the left ventricle, interventricular septum, coronary trunk, left anterior descending artery (LAD), circumflex artery and right coronary artery), were analyzed for both treatment plans for 9 out of the 12 patients enrolled.

Paired two- sided Wilcoxon’s signed -rank test was performed for all dosimetric parameters with a 5% significance level, using R software (v. 1.2.5042).

We have also collected on CT slices minimum distance between PTV and heart and the same parameter to the isocenter slice.

Results:

The analysis of data from this prospective trial has proven a statistically significant dosimetric benefit derived from the use of CPAP in adjuvant RT for left-sided breast cancer, both in terms of Dmean and Dmax, to the heart and all cardiac substructures (p<0.001), especially to the LAD (Fig. 1), linked to an increased distance between heart and PTV (Fig. 2). The results have also shown a statistically significative difference in lungs volume in favor of using CPAP (p<0.001), with a median difference of 1382.2 cc as compared to FB median lungs volume. Using 4D technique the maximum percentage deviation between the 10 different respiratory phases for all the patients was found to be less than 5%.