Internal mammary node irradiation in 4541 node-positive breast cancer patients treated with newer systemic therapies and 3D-based radiotherapy (DBCG IMN2): a prospective, nationwide, population-based cohort study

Anders W. Mølby Nielsen*, Lise B. J. Thorsen, Demet Özcan, Louise W. Matthiessen, Else Maae, Marie L. H. Milo, Mette H. Nielsen, Trine Tramm, Jens Overgaard, Birgitte V. Offersen, DBCG RT Committee

*Kontaktforfatter

Publikation: Bidrag til tidsskriftTidsskriftartikelForskningpeer review

2 Citationer (Scopus)
17 Downloads (Pure)

Abstract

Background
Internal mammary node irradiation (IMNI) improves overall survival (OS) in node-positive breast cancer patients. However, the effect is not documented in breast cancer patients treated with newer systemic therapies and 3D-based radiotherapy (RT). Therefore, the Danish Breast Cancer Group (DBCG) IMN2 study aimed to investigate the effect of IMNI in node-positive breast cancer patients treated with newer systemic therapies and 3D-based RT.

Methods
DBCG IMN2 was a nationwide population-based cohort study prospectively allocating node-positive breast cancer patients with right-sided tumours to IMNI and patients with left-sided tumours to no IMNI in six RT centres. Exclusion criteria were prior malignancies, bilateral breast cancer, neoadjuvant systemic therapy, recurrence before RT, or non-standard RT. Systemic treatment included taxane-based chemotherapy, aromatase inhibitors, and trastuzumab. The primary end-point was OS. Secondary endpoints were breast cancer mortality and distant metastasis. Cox regression analyses were used for adjusted hazard ratios (HR). Clinicaltrial.gov ID: NCT06549920.

Findings
In the period January 2007–May 2014, a total of 4541 patients were included. Patient characteristics were distributed evenly between right- and left-sided patients. Median follow-up was 13.7 years for OS. Survival rates at 15 years were 65.0% in patients with IMNI and 60.8% without leading to an adjusted HR of 0.85 (95% CI, 0.76–0.94; p = 0.0016) for OS. Corresponding HRs were 0.84 (95% CI, 0.74–0.95; p = 0.0077) for breast cancer mortality and HR 0.87 (95% CI, 0.78–0.98; p = 0.026) for distant metastasis. No subgroups were identified for the omission of IMNI. The 15-year cumulative incidence of death from ischemic or valvular heart disease was 0.2% (95% CI, 0.0–0.5) in right-sided and 0.7% (95% CI, 0.4–1.2) in left-sided patients.

Interpretation
IMNI reduced distant metastasis and breast cancer mortality and improved OS in node-positive breast cancer patients, despite treatment with newer systemic therapies and 3D-based RT.

Funding
This work was supported by the Danish Cancer Society and Department of Clinical Medicine, Aarhus University, Denmark.
OriginalsprogEngelsk
Artikelnummer101160
TidsskriftThe Lancet Regional Health - Europe
Vol/bind49
Antal sider10
ISSN2666-7762
DOI
StatusUdgivet - feb. 2025

Bibliografisk note

© 2024 The Author(s).

Fingeraftryk

Dyk ned i forskningsemnerne om 'Internal mammary node irradiation in 4541 node-positive breast cancer patients treated with newer systemic therapies and 3D-based radiotherapy (DBCG IMN2): a prospective, nationwide, population-based cohort study'. Sammen danner de et unikt fingeraftryk.

Citationsformater