ESTRO 2025 - Abstract Book

S559

Clinical - Breast

ESTRO 2025

approach. Ongoing follow-up willevaluate long-term outcomes, including recurrence, cosmetic results, and patient reported quality of life.

Keywords: DCIS, APBI

References: 1. Radiotherapy in breast-conserving treatment for ductal carcinomain situ: first results of the EORTC randomised phase III trial 10853. J, Julien. s.l. : Lancet, 2000, Vol. 355 (92003, p. 528-533. 2. Accelerated partial breast irradiation for pure ductal carcinoma in situ. SS, Park. s.l. : Int J Radiat Oncol Biol Phys, 2011, Vol. 81(2), p. 403-408. 3. External accelerated partial breast irradiation for ductal carcinoma in situ: long-term follow-up from a phase 3 randomized trial. C, Becherini. s.l. : Tumori, 2019, Vol. 105(3), p. 205-209. 4. The role of boost and hypofractionation as adjuvant radiotherapy in patients with DCIS: a meta-analysis of observational studies. C, Nilsson. s.l. : Radiother Oncol, 2015, Vol. 114(1), p. 50-55.

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Digital Poster Radiation-Induced Lung Disease in Breast Cancer Patients Treated with TomoTherapy: A Retrospective Comparison of TomoDirect and TomoHelical Modes

Adeodatus Vito S. Nicanor, Bianca Nikkola Olonan, Janel Aira Mendoza Radiology - Radiation Oncology, Makati Medical Center, Makati, Philippines

Purpose/Objective: Radiation therapy is essential for reducing local recurrences and improving survival in patients with locally advanced breast cancer. Emerging radiotherapy techniques focus on enhancing treatment precision while minimizing radiation-induced damage to surrounding organs. One of the most common complications these advancements aim to prevent is radiation-induced lung injury (RILD), which, though often asymptomatic, can have significant consequences. TomoTherapy, an advanced image-guided, intensity-modulated radiotherapy system, offers two delivery modes: TomoDirect and TomoHelical, which differ in the way radiation is administered. In this study, we aimed to evaluate radiographic RILD findings with TomoTherapy and investigate whether the TomoHelical mode, compared to TomoDirect, increases the risk of radiographic abnormalities associated with RILD in breast cancer patients. Material/Methods: We conducted a retrospective analysis involving breast cancer patients treated with TomoTherapy from 2014 to 2018 at a tertiary hospital in Metro Manila. Patients were categorized based on treatment mode (TomoDirect or TomoHelical). We examined clinical and radiotherapy parameters to assess their influence on RILD occurrence, focusing on radiographic findings. Results: Of the 119 patients treated with TomoTherapy, a total of twenty-eight patients (23.5%) had radiographic RILD findings, twelve (42.9%) were found to have RILD ipsilateral to the site of radiotherapy, eleven (39.3%) had bilateral lung involvement, and five (17.9%) had contralateral lung involvement. Contralateral lung involvement only occurred in the TomoHelical mode, and bilateral lung involvement was more commonly seen in the TomoDirect mode. Importantly, no significant difference in RILD occurrence was observed between TomoDirect (18.5%) and TomoHelical (27.7%) modes. However, TomoHelical mode patients exhibited higher odds of developing RILD (1.8 times) compared to TomoDirect mode, though statistical significance was not reached. Specific associations were identified, including radiation therapy target volume (chest wall radiation vs. whole breast radiation, p=0.047), regional nodal irradiation (full regional nodal irradiation vs. axillary nodal irradiation only, p=0.047), and post-