Main Session
Sep
28
PQA 04 - Breast Cancer, Patient Reported Outcomes/QoL/Survivorship, Functional Radiation Medicine, Hematologic Malignancies, Palliative Care, and International/Global Oncology
2829 - Cardiopulmonary Dosimetric Analysis of Radiotherapy Techniques Using an Ultra-Hypofractionated Regimen for Left-Sided Breast Cancer: A Latin American Single-Center Experience
Presenter(s)
Guillermo Pacheco-Gutierrez, MD - Instituto Nacional de Cancerologia, Mexico City, Distrito F
G. Pacheco-Gutierrez, C. H. Flores Balcazar, R. Ramos Prudencio, A. D. Cruz Cortes, J. Linares, and A. Poitevin; Medica Sur, Mexico City, Mexico
Purpose/Objective(s):
To perform a dosimetric comparison of cardiac, left lung and left anterior descending artery (LAD) doses among different radiotherapy techniques in patients with left-sided breast cancer treated with an ultra-hypofractionated regimen.Materials/Methods:
We conducted a retrospective dosimetric analysis of 26 patients with left-sided breast cancer treated with breast-conserving surgery and adjuvant radiotherapy using 26 Gy in 5 fractions under deep inspiration breath hold (DIBH). Patients receiving no boost, sequential boost or simultaneous integrated boost were included. Treatment technique was selected at the discretion of the treating radiation oncologist and included 3D conformal radiotherapy (3DCRT), VMAT or a hybrid approach (3DCRT + VMAT). Dosimetric parameters analyzed for the heart included Dmean, Dmax and V1.5; Dmean and V8 for the left lung; and Dmean, Dmax and V15 for the LAD.Results:
Between 2022 and 2025, 48 patients with breast cancer were treated with the 26 Gy in 5 fractions regimen under DIBH at our institution. Of these, 26 with left-sided disease were selected for dosimetric analysis. Ten patients received sequential or simultaneous integrated boost; no significant impact on LAD, heart or left-lung doses was observed. 3DCRT demonstrated the lowest mean heart dose compared with VMAT but was associated with higher cardiac maximum doses. VMAT resulted in increased low-dose exposure to the heart and left lung, reflected by higher V1.5 and V8 values. Hybrid planning achieved lower cardiac and pulmonary low-dose volumes compared with VMAT while reducing high-dose cardiac hotspots relative to 3DCRT. For the LAD, 3DCRT showed the highest mean dose, whereas VMAT and hybrid techniques achieved lower mean exposure. LAD maximum dose and V15 followed a similar pattern, with 3DCRT demonstrating higher peak doses than hybrid and VMAT. Overall, hybrid strategy provided the most balanced cardiopulmonary profile among techniques.Conclusion:
In patients with left-sided breast cancer treated with ultra-hypofractionation under DIBH, radiotherapy technique significantly influences dose distribution. Although 3DCRT minimized mean heart dose, it increased LAD mean and maximum doses. VMAT reduced high-dose LAD exposure but increased low-dose cardiac and pulmonary volumes. Hybrid planning demonstrated the most favorable overall cardiopulmonary balance. These findings suggest that hybrid approaches may help reduce LAD exposure while limiting low-dose spread to the heart and lung, warranting further evaluation in larger cohorts.