ESTRO 2024 - Abstract Book

S488

Clinical - Breast

ESTRO 2024

576

Digital Poster

Nodal boost in breast cancer patients with PET positive nodes in addition to adjuvant radiotherapy

Marie Louise Holm Milo 1,2 , Ingelise Jensen 3 , Mette Møller 1 , Ursula Gerda Inge Falkmer 1,2

1 Aalborg Universitets Hospital, Department of Oncology, Aalborg, Denmark. 2 Aalborg University, Faculty of Medicine, Aalborg, Denmark. 3 Aalborg Universitets Hospital, Department of Medical Physics, Aalborg, Denmark

Purpose/Objective:

In breast cancer (BC) patients diagnosed with locally advanced breast cancer (LABC), a PET-CT scan is often used for excluding metastatic disease before neoadjuvant/adjuvant treatment. The PET-CT scan may visualize PET-positive lymph nodes (LN) in regional LNs not available for surgery (level 3, 4, interpectoral and internal mammary nodes (IMN)). In Denmark, there is no consensus guidelines regarding LN boost in addition to adjuvant radiation therapy (RT). The aim of this study was to investigate the extent of LN boost, the RT dose delivered, and image used for planning in LABC patients with PET-positive LNs not available for surgery.

Material/Methods:

A retrospective study of LABC patients treated with one or more LN boosts in addition to adjuvant RT at Aalborg University Hospital from June 2018 to May 2023, was conducted. Information on patient characteristics and treatment were obtained from the patient records and the RT planning CT scans. Descriptive analyses of patient and tumor characteristics and RT treatment, including LN boosts, were performed.

Results:

In total, 18 LABC patients received minimum one LN boost in addition to locoregional adjuvant RT during a period of 5 years. The median age was 52 years (range 26-87 years). Eight patients (44%) were diagnosed with triple negative disease and 16 patients received chemotherapy (13 neoadjuvant, 3 adjuvant). The RT dose to the chest wall/breast and regional LNs was 50 Gy in 25 fractions (50%) or 40 Gy in 15 fractions (50%). The patients received 1 to 4 boost areas, thus, 30 boost areas were identified with IMN being the most common localization (table 1). The sequential LN boosts were delivered with 10 Gy in 5 fractions (90%) or 16 Gy in 8 fractions (10%). The LN boosts were delineated as a gross tumor volume (GTV) in the involved level in 63% of the cases while the whole level was delineated in 37% of the cases. The LN boosts were often defined from the pre-chemotherapy PET-CT scan, however, in the last two years, a post-chemotherapy/surgery PET-CT may have been performed.

Table 1: LN-boost areas for the 18 patients, who in total received 30 boosts.

LN-boost area

Number of boosts, n (%)

Internal mammary nodes (IMN)

9 (30)