• André Fortin, Anne Dagnault, Lucie Blondeau, Thi Trinh Thuc Vu, and Marie Larochelle.
• Department of Radiation Oncology, L'Hôtel-Dieu de Québec, Québec City, Québec, Canada. afortin@videotron.ca
• Int. J. Radiat. Oncol. Biol. Phys. 2006 May 1; 65 (1): 33-9.

PurposeAfter breast-conserving surgery, recommendations for regional nodal radiotherapy are usually based on the number of positive nodes. This number is dependent on the number of nodes removed during the axillary dissection. This study examines whether the percentage of positive nodes may help to select patients for regional radiotherapy.Methods And MaterialsA retrospective study was conducted on 1,372 T1-T2 node-positive breast cancer patients treated at L'Hôtel-Dieu de Québec Hospital between 1972 and 1997.ResultsAmong the patients who did not receive regional radiotherapy, the percentage of involved nodes was significantly associated with axillary failure. Ten-year axillary control rates were 97% and 91% when the percentage of involved nodes was <50% and > or =50%, respectively (p = 0.007). In addition, regional radiotherapy is always significantly associated with a decrease in overall regional failure (axillary and/or supraclavicular), regardless of the percentage of involved nodes. However, regional radiotherapy reduced the axillary failure rate (2% vs. 9%, p = 0.007) only when more than a specific percentage of nodes was involved (> or =40% if N1-3 and > or =50% if N>3 nodes).ConclusionsThe percentage of involved nodes should be taken into consideration in selecting patients for regional radiotherapy. Irradiation of the axilla should be reserved for patients with a specific ratio: >40% involved nodes if N1-3 and > or =50% involved nodes if N>3 nodes.

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