International Journal of Radiation Oncology*Biology*Physics
Clinical investigationBreastThe impact of the number of excised axillary nodes and of the percentage of involved nodes on regional nodal failure in patients treated by breast-conserving surgery with or without regional irradiation
Introduction
In patients with invasive breast carcinoma treated by modified radical mastectomy, the number of nodes removed during axillary dissection has been shown to have an impact on the rate of regional nodal failure. In studies where the median number of nodes removed was seven, a substantial number of patients had a failure in the incompletely dissected axilla (1, 2). In contrast, in studies where the median number of nodes removed was >12, failure in the axilla was a rare event, even in the absence of radiotherapy (3, 4). Based on these results, it has been recommended that patients with an incompletely dissected axilla and with more than three positive nodes receive radiation to the axillary and supraclavicular areas. In patients with a complete axillary dissection, only the supraclavicular area should be irradiated (5).
After breast-conserving surgery, regional nodal radiotherapy has been shown to also be beneficial for certain patients. Indeed, studies have shown that in node-positive patients, the rate of regional failure was significantly lower with regional radiotherapy compared with breast irradiation alone (6, 7). However, it is not clear which nodal groups should be irradiated. Irradiation of the axilla may be unnecessary for some patients, i.e., those who have received a complete axillary dissection. Unfortunately, there are no guidelines on this issue, and treatment policies are not uniform (8). Based on results from the postmastectomy series (see above), it has been recommended that patients with an incomplete axillary dissection and with more than three positive nodes receive axillary irradiation.
One concern, however, is that all recommendations regarding regional radiotherapy are based on the number of positive nodes, a number that is dependent on the number of nodes removed during the axillary dissection (9). It is possible that the percentage of positive nodes represents a more accurate predictor of axillary failure than the absolute number of positive nodes. Models that attempt to predict the risk of having ≥3 positive nodes when the actual number of positive nodes is <3 are currently in development (10).
The first aim of this study was to determine whether the number of nodes removed during axillary dissection (or the percentage of positive nodes) has an impact on axillary failure in patients receiving breast irradiation only. The second aim was to evaluate the benefit of regional radiotherapy as a function of the percentage of nodes involved.
Section snippets
Methods and materials
A retrospective study was conducted on all node-positive breast cancer patients treated at L’Hôtel-Dieu de Québec between 1972 and 1997. This cohort of 1,372 women was fully described in a previous article (6). Briefly, all node-positive patients with stage T1–T2 invasive breast carcinoma who had received at least 44 Gy to the breast were included. The following data were compiled when available: age, menopausal status, pathologic stage, histologic type and grade, surgical margin status,
Part 1: The relationship between the number of positive nodes, the number of nodes removed, and the percentage of positive nodes
This section includes all the node-positive patients who received regional radiotherapy (477 patients) or not (904 patients). The relationship between the number of positive nodes and number of nodes removed is shown in Fig. 1. The number of positive nodes was directly proportional to the number of nodes removed (p < 0.00001). As a rule of thumb, for each five additional nodes removed, one more positive node could be found.
Percentage of positive nodes is defined as the quotient of positive
Discussion
Some important results stem from this study. First, the number of nodes removed does not have an impact on axillary failure in node-positive patients treated by breast- conserving surgery and radiotherapy to the breast alone. Second, the percentage of involved nodes is associated with axillary failure. In patients with >40% (for N1–3 positive nodes) and >50% (for N > 3 positive nodes) involved nodes, the rates of axillary failure are significantly increased. Moreover, in these groups of
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