ESTRO 2024 - Abstract Book

S578

Clinical - Breast

ESTRO 2024

Material/Methods:

Thirty-two BC patients with positive IMLN treated between 2013-2022 were retrospectively evaluated. RT boost to IMLN was administered either with a sequential or a simultaneous integrated boost (SIB) technique. The treatment outcomes, prognostic factors, and toxicity profile were analyzed.

Results:

All patients received some form of systemic treatment before or after surgery or RT. Complete (CR) and partial response (PR) to systemic treatment in IMLN was observed in 20 (64%) and 7 (23%) patients, respectively. One (3%) and 3 (10%) patients had stable or progressive disease in IMLN after systemic treatment. Ten (91%) of 11 patients who had a residual IMLN before RT, had a CR in IMLN after RT. With a median follow-up of 62 months, 1 (3%), 5 (16%), and 2 (6%) patients had regional recurrence (RR) alone, distant metastasis (DM) alone, and both RR and DM, respectively. RR was observed at IMLN in 1 patient and supraclavicular fossa in 2 patients. Five-year overall survival (OS), disease-free survival (DFS), locoregional recurrence-free survival (LRRFS), and distant metastasis-free survival (DMFS) was 84%, 67%, 80%, and 70%, respectively. CR or PR to systemic treatment in IMLNs, presence of extracapsular extension in axillary LNs, and boost technique for IMLN were strong predictors for survival. The RT boost with SIB technique to IMLN improved OS and DFS compared to sequential boost technique. Late cardiac toxicity was moderately higher in patients with left-sided tumor than those with right sided tumor (14% vs. 0%, p=0.290). Boost technique did not affect organ at risk doses and cardiac toxicity.

Conclusion:

RT boost to IMLN without surgical resection provides excellent oncological outcomes with acceptable toxicity profile and can be performed even in BC patients with left-sided tumor. SIB technique can also be used for RT boost to IMLN without additional toxicity.

Keywords: IMLN metastasis, radiotherapy, boost technique

References:

1. Poortmans PM, Weltens C, Fortpied C, Kirkove C, Peignaux-Casasnovas K, Budach V, van der Leij F, Vonk E, Weidner N, Rivera S et al: Internal mammary and medial supraclavicular lymph node chain irradiation in stage I-III breast cancer (EORTC 22922/10925): 15-year results of a randomised, phase 3 trial. Lancet Oncol 2020, 21(12):1602 1610. 2. Andring LM, Diao K, Sun S, Patel M, Whitman GJ, Schlembach P, Arzu I, Joyner MM, Shaitelman SF, Hoffman K et al: Locoregional Management and Prognostic Factors in Breast Cancer With Ipsilateral Internal Mammary and Axillary Lymph Node Involvement. Int J Radiat Oncol Biol Phys 2022, 113(3):552-560.