ESTRO 2024 - Abstract Book

S516

Clinical - Breast

ESTRO 2024

2. Paul McGale et al. Incidence of heart disease in 35,000 women treated with radiotherapy for breast cancer in Denmark and Sweden. Radiother Oncol. 2011 Aug;100(2):167-75.

3. Carolyn W Taylor et al. Cardiac dose estimates from Danish and Swedish breast cancer radiotherapy during 1977 2001. Radiother Oncol. 2011 Aug;100(2):176-83.

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Digital Poster

outcomes and defects of Intraoperative radiotherapy with electron beams in breast cancer patients

Tanun Jitwatcharakomol 1 , Jiraporn Setakoranukul 1 , Kullathorn Thephamongkhol 1 , Suebwong Chuthatisith 2 , Adune Ratanawichitrasin 2 , Naponwan Sirima 3 1 Faculty of Medicine, Siriraj Hospital, Mahidol University, Radiation Oncology, Bangkok, Thailand. 2 Faculty of Medicine, Siriraj Hospital, Mahidol University, Surgery, Bangkok, Thailand. 3 Faculty of Medicine, Siriraj Hospital, Mahidol University, Radiation Diagnostic, Bangkok, Thailand

Purpose/Objective:

Intraoperative radiotherapy (IORT) with electron was found to be higher ipsilateral breast tumor recurrence (IBTR) compared with external beam radiotherapy in large-scale randomized control trials. Retrospective studies suggested that it could be an alternative option in the suitable group of patients classified by ASTRO consensus. However, in real-world data, it seems impossible to classify the patient groups before surgery since lots of factors will be reported in post-excision pathological results. The objective of this study is to report the oncological outcomes of IORT with electron beams using our pre-excision criteria.

Material/Methods:

This was a retrospective, single-center, single-arm study. All early-stage breast cancer patients received IORT with electron beams that fulfilled our pre- excision criteria including age ≥ 55 years, tumor size ≤ 2 cm, Estrogen receptor (ER) positive, no angiolymphatic space invasion (LVSI), ductal carcinoma histology, no multicentric tumor, and sentinel lymph node-negative on the frozen section was reviewed. The primary outcome was 5-year local control (LC), whereas the secondary outcomes were 5-year locoregional control (LRC), 5-year distant metastasis-free survival (DMFS), and pattern of failure

Results:

From January 2011 to December 2022, 126 patients were included in this study. After reviewing post-excision pathological results, patients were classified by ASTRO consensus into suitable groups (58.73%), cautionary groups (35.71%), and unsuitable groups (5.56%). The median follow-up time was 6.7 years. For the whole population, the 5 year of local control and locoregional control was 98.16%, 95%CI [92.81%-99.54%], and 96.36%, 95% CI [90.58%-