ESTRO 2024 - Abstract Book

S4355

Physics - Intra-fraction motion management and real-time adaptive radiotherapy

ESTRO 2024

Sawanya Suwandee, Jiraporn Setakoranukul, Kullathorn Thephamongkhol, Utumporn Puangragsa, Ukrit Choochinprakarn

Division of Radiation Oncology, Department of Radiology,Faculty of Medicine, Siriraj Hospital, Bangkok, Thailand

Purpose/Objective:

Postoperative radiotherapy in breast cancer patients is an essential treatment to reduce the risk of loco-regional recurrences and improve long-term survival. With benefit of survival improvement, breast radiotherapy become a standard treatment for early-stage breast cancer. However, radiotherapy for left-sided breast cancer with a high mean heart dose could result in increased mortality and secondary cardiac events. The majority method that has been used is deep inspiration breath hold (DIBH). This method utilizes voluntary breathing which increase the lung volume to separate heart from the chest wall. Nowadays, DIBH technique has been used in multiples publications and found that method reduce the heart dose and ipsilateral lung without compromising target coverage. Although DIBH is a helpful technique to improve left breast radiotherapy, some patient who cannot control their breath for DIBH, especially elder patients or irregular breathing pattern patients, are unable to achieve success with this method, resulting in poor compliance and a higher heart dose. An alternative innovative technique to reproduce the patient anatomy and tumor motion management associated with DIBH using Continuous positive airway pressure (CPAP) was introduced. The system uses an CPAP accessory to administer of positive pressure to airways during breathing entire respiratory cycle. This study aimed to evaluate the relationship between CPAP positive pressure with mean heart dose in DIBH technique. Twenty-three patients with left-sided breast cancer were trained prior CT simulation by wearing the CPAP mask and acclimatize to positive pressure. The patient was placed on breast board in supine position and wearing a CPAP mask with gradually increased to target pressure of 10 to 14 cmH2O. After that, the patients were underwent CT simulation with free breathing(FB) condition, and then CT simulation with CPAP positive pressure. All CT images data were imported to treatment planning system for planning with conventional dose 2 Gy in 25 fractions. To reduce variation of contouring and treatment planning, the contouring using the automated atlas-based contouring delineated Clinical target volume (CTV) left breast with Planning target volume (PTV) expansion of 5 mm were planned by automated breast planning function. Two tangential fields with subfields were improve homogeneity and avoid hot spots for PTV breast to utilize the 95% of PTV coverage with 95% of the prescription dose. The dosimetric data in mean heart dose, Heart V25%, mean LAD, max LAD, CPAP positive pressure, left lung V20%, heart and left lung volume were collected. Material/Methods:

Results: