ESTRO 2024 - Abstract Book

S634

Clinical - Breast

ESTRO 2024

Seoul, Korea, Republic of. 6 Proton Therapy Center, National Cancer Center, Radiation Oncology, Goyang, Korea, Republic of. 7 Seoul National University Bundang Hospital, Seoul National University College of Medicine, Radiation Oncology, Seongnam, Korea, Republic of. 8 Eunpyeong St. Mary’s Hospital, College of Medicine, The Catholic University of Korea, Radiation Oncology, Seoul, Korea, Republic of. 9 Chonnam National University Hospital, Chonnam National University Medical School, Radiation Oncology, Gwangju, Korea, Republic of. 10 Ewha Womans University Mokdong Hospital, Ewha Womans University College of Medicine, Radiation Oncology, Seoul, Korea, Republic of. 11 Soonchunhyang University Seoul Hospital, Soonchunhyang University College of Medicine, Radiation Oncology, Seoul, Korea, Republic of. 12 Chungnam National University Hospital, Chungnam National University College of Medicine, Radiation Oncology, Daejeon, Korea, Republic of. 13 Hanyang University Hospital, Hanyang University College of Medicine, Radiation Oncology, Seoul, Korea, Republic of

Purpose/Objective:

Adenoid cystic carcinoma (ACC) of the breast is an uncommon malignant tumor, and there is limited data available regarding its treatment outcomes and recurrence patterns per treatment modalities. This study, conducted across multiple institutions, aims to evaluate the treatment approaches and locoregional patterns for primary ACC in the breast. (KROG 22-14)

Material/Methods:

A total of 111 patients diagnosed with primary ACC in the breast between 1992 and 2022 were collected from multi institutions. All patients underwent surgical resection, including breast-conserving surgery (BCS) or total mastectomy (TM). The recurrence patterns and locoregional recurrence-free survival (LRFS) were assessed. Eighteen patients were excluded due to incomplete information, resulting in a final analysis of 93 patients.

Results:

Seventy-five patients (80.7%) underwent BCS, and 71 of them (94.7%) received adjuvant radiation therapy (RT). Eighteen patients (19.3%) underwent TM, with 5 of them (27.8%) also receiving adjuvant RT. With a median follow up of 50 months, the rates of LRFS were 94.0% at 3 years and 84.2% at 5 years. Local recurrence (LR) was observed in 5 patients (5.4%). Most LR occurred in the tumor bed (N=4, 80%). Three of LR (60%) had a history of BCS followed by RT, meanwhile, two of LR (40%) had a history of mastectomy with (N=1) and without (N=1) adjuvant RT. Regional recurrence occurred in 2 patients (2.2%), and both cases had a history of RT with (N=1) and without (N=1) irradiation of the regional lymph nodes. RT showed no significant association with LRFS in patients who underwent BCS (p=0.96). Also, partial breast irradiation (p=0.35) and BCS (p=0.96) had no significant association with LRFS. Distant metastasis occurred in 12 patients (12.9%), primarily in the lungs (N=10).

Tumor size (cm)

Resection margin

Adjuvant treatment

Recurred Site

No

Age

pN

Surgery

ER/PR/HER2 Ki-67 (%)

1

74

2.2

0

-

BCS+SLNB -/-/-

20

CTx+RT

Tumor