2949 - Evaluation of New SGRT-Based Approach to DIBH for Left-Sided Breast Cancers on a Helical Delivery Platform

03:00pm - 04:00pm PT

Hall F

Screen: 20

POSTER

Presenter(s)

Sanjay Hunugundmath, MD - Sahyadri Hospital, Pune, Maharashtr

S. Hunugundmath¹, M. Deputy¹, A. Nirhali¹, V. Naik², and S. Gadhve³; ¹sahyadri superspecialty hospital, pune, India, ²Amrita institute of medical sciences, Kochi, Kerala, India, ³sahaydri hospitals, pune, India

Purpose/Objective(s): Deep-inspiration breath-hold (DIBH) is a well-established technique for reducing cardiac morbidity and lung injury in left breast cancer treatments by moving the radiation field away from the heart by inflating the lungs. While this approach has been studied at length for C-arm linacs, there is a lack of evidence to support its utility on a helical delivery platform. We report on what we believe to be the 1st cohort of left-sided breast cancer patients to be treated via DIBH on a helical platform using a surface guided system (SGRT-h). We provide a dosimetric comparison with our clinic’s standard DIBH technique – respiration-control delivered on a C-arm linac (RC-c). Also, we evaluate patient comfort and ease of use on both systems.

Materials/Methods: Patients who underwent left breast conservation surgery followed by breast radiotherapy and who could hold their breath for at least 20 s were considered for this procedure. 20 consecutive patients were included in the study. All patients underwent 3-day training for both SGRT-h and RC-c systems between Sept 2024 - Feb 2025 at our center. Upon completion of training, patients were provided with a questionnaire to assess their comfort and system ease of use. Simulation scans were acquired for both techniques and treatment plans were generated. The prescribed dose (DRX) was 40 Gy in 15 fractions and 95% of the target had to receive > 95% DRX. Organ at risk (OAR) constraints were followed based on RTOG guidelines. Mann-Whitney U statistical test was used, and level of significance was set at < 0.05

Results: All 20 patients were treated using the SGRT-h technique. The mean breathhold duration was 22 s. Target coverage goals were met for all plans and did not differ between groups. All OAR constraints were satisfied. There was a statistically significant difference in the mean heart dose (150 cGy and 275 cGy for SGRT-h and RC-c respectively, (p<0.007)) and in the heart V30 (0.4% and 5.5% for SGRT-h and RC-c respectively (p<0.03)). There was a trend towards lower mean LAD dose with SGRT-h (225 cGy compared to 275 cGy), however this failed to reach statistical significance (p<0.20). Similarly, a trend towards lower ipsilateral lung V5 and V20 was observed with SGRT-h (40.2 %and 16.3% respectively) compared to RC-c (50.4%and 21.7%), however this was not statistically significant. The questionnaire revealed that patients found the instructions for SGRT-h easier to understand and the treatment less restrictive.

Conclusion: We reported on the 1st cohort of left-breast cancer patients treated with DIBH on a helical system using SGRT. Compared to our previous standard approach, this implementation offers superior dosimetry, with a significant reduction in both mean heart and LAD doses, a trend towards lower lung dose, and a higher level of patient satisfaction. We conclude that this novel implementation of DIBH can be adopted clinically.