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Abstract

PURPOSE:

It is unknown whether irradiation of the internal mammary lymph nodes improves survival in patients with early-stage breast cancer. A possible survival benefit might be offset by radiation-induced heart disease. We assessed the effect of internal mammary node irradiation (IMNI) in patients with early-stage node-positive breast cancer.

PATIENTS AND METHODS:

In this nationwide, prospective population-based cohort study, we included patients who underwent operation for unilateral early-stage node-positive breast cancer. Patients with right-sided disease were allocated to IMNI, whereas patients with left-sided disease were allocated to no IMNI because of the risk of radiation-induced heart disease. The primary end point was overall survival. Secondary end points were breast cancer mortality and distant recurrence. Analyses were by intention to treat.

RESULTS:

A total of 3,089 patients were included. Of these, 1,492 patients were allocated to IMNI, whereas 1,597 patients were allocated to no IMNI. With a median of 8.9 years of follow-up time, the 8-year overall survival rates were 75.9% with IMNI versus 72.2% without IMNI. The adjusted hazard ratio (HR) for death was 0.82 (95% CI, 0.72 to 0.94; P = .005). Breast cancer mortality was 20.9% with IMNI versus 23.4% without IMNI (adjusted HR, 0.85; 95% CI, 0.73 to 0.98; P = .03). The risk of distant recurrence at 8 years was 27.4% with IMNI versus 29.7% without IMNI (adjusted HR, 0.89; 95% CI, 0.78 to 1.01; P = .07). The effect of IMNI was more pronounced in patients at high risk of internal mammary node metastasis. Equal numbers in each group died of ischemic heart disease.

CONCLUSION:

In this naturally allocated, population-based cohort study, IMNI increased overall survival in patients with early-stage node-positive breast cancer.

Author information

Thorsen LB1, Offersen BV2, Danø H2, Berg M2, Jensen I2, Pedersen AN2, Zimmermann SJ2, Brodersen HJ2, Overgaard M2, Overgaard J2.​

1Lise Bech Jellesmark Thorsen, Birgitte Vrou Offersen, Marie Overgaard, and Jens Overgaard, Aarhus University Hospital, Aarhus; Hella Danø, Herlev Hospital, Herlev; Martin Berg, Vejle Hospital, Vejle; Ingelise Jensen, Aalborg University Hospital, Aalborg; Anders Navrsted Pedersen, Rigshospitalet, Copenhagen; Sune Jürg Zimmermann, Odense University Hospital, Odense, Denmark; and Hans-Jürgen Brodersen, St Franziskus-Hospital, Flensburg, Germany. liseb@oncology.au.dk.

2Lise Bech Jellesmark Thorsen, Birgitte Vrou Offersen, Marie Overgaard, and Jens Overgaard, Aarhus University Hospital, Aarhus; Hella Danø, Herlev Hospital, Herlev; Martin Berg, Vejle Hospital, Vejle; Ingelise Jensen, Aalborg University Hospital, Aalborg; Anders Navrsted Pedersen, Rigshospitalet, Copenhagen; Sune Jürg Zimmermann, Odense University Hospital, Odense, Denmark; and Hans-Jürgen Brodersen, St Franziskus-Hospital, Flensburg, Germany.