Internal mammary nodes irradiation prolongs survival in breast cancer

The addition of internal mammary nodal irradiation (IMNI) in the treatment of breast cancer leads to better overall survival (OS), disease-free survival (DFS), distant metastasis-free survival (DMFS), and lower breast cancer mortality (BCM), reveals a study. In addition, patients with pN+ and medial/central tumour location achieved the best OS from IMNI.

Study authors performed a literature search of prospective studies comparing IMNI to no IMNI and subgroup analyses for tumour location (medial/central vs lateral) and nodal status (pN+ vs pN0). They used fixed-effect model if there was no heterogeneity and random-effects model otherwise.

OS was the primary endpoint, while secondary ones included local recurrence, regional recurrence, DFS, BCM, DMFS, grade 2+ skin toxicity, cardiac events, and pneumonitis events.

Four studies met the eligibility criteria, with a total of 5,258 patients (IMNI: n=2,592; control: n=2,666).

Pooled analysis revealed that the inclusion of IMNI prolonged OS for all-comers (hazard ratio [HR], 0.89, 95 percent confidence interval [CI], 0.81‒0.97; p=0.008) and in subgroups of pN+ with medial/central tumour location (HR, 0.84, 95 percent CI, 0.73‒0.96; p=0.01) and pN+ with lateral tumour location (HR, 0.87, 95 percent CI, 0.77‒0.99; p=0.04).

No significant difference in OS was observed in subgroups of pN0 and medial/central tumour location.

Local recurrence did not differ between IMNI and no IMNI, but regional recurrence showed an improvement with IMNI (p=0.04). Improvements were also noted for DFS (HR, 0.91, 95 percent CI, 0.84‒0.99; p=0.03), BCM (HR, 0.87, 95 percent CI, 0.77‒0.98; p=0.03), and DMFS (HR, 0.87, 95 percent CI, 0.78‒0.98; p=0.02).

In addition, “grade 2+ skin toxicity, cardiac events, and pneumonitis events were not significantly different between patients in the IMNI and no IMNI groups,” the authors said.