Clinical investigation
Breast
The 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

https://doi.org/10.1016/j.ijrobp.2005.12.014Get rights and content

Purpose: After 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 Materials: A 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.

Results: Among 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 ≥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 (≥40% if N1–3 and ≥50% if N>3 nodes).

Conclusions: The 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 ≥50% involved nodes if N>3 nodes.

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

References (30)

  • J. Yu et al.

    The pattern of lymphatic metastasis of breast cancer and its influence on the delineation of radiation fields

    Int J Radiat Oncol Biol Phys

    (2005)
  • P.T. Truong et al.

    Selecting breast cancer patients with T1–T2 tumors and one to three positive axillary nodes at high postmastectomy locoregional recurrence risk for adjuvant radiotherapy

    Int J Radiat Oncol Biol Phys

    (2005)
  • D.B. Kingsmore et al.

    Axillary recurrence in breast cancer

    Eur J Surg Oncol

    (2005)
  • M. Overgaard et al.

    Postoperative radiotherapy in high-risk premenopausal women with breast cancer who receive adjuvant chemotherapy. Danish Breast Cancer Cooperative Group 82b Trial

    N Engl J Med

    (1997)
  • A. Recht et al.

    Locoregional failure 10 years after mastectomy and adjuvant chemotherapy with or without tamoxifen without irradiationexperience of the Eastern Cooperative Oncology Group

    J Clin Oncol

    (1999)
  • Cited by (43)

    • A clinical perspective on regional nodal irradiation for breast cancer

      2017, Breast
      Citation Excerpt :

      Several clinicopathologic features can aid in the characterization of the spectrum. Besides pathologic nodal staging, the lymph node ratio (LNR), or the proportion of involved nodes to total number of dissected nodes, has been found to be an independent predictor of OS and is linked to the risk of axillary failure in the patients with cT1-2, node-positive breast cancer treated without RNI [24,25]. Other more well known risk factors that can contribute to sufficiently high LRR estimates to warrant RNI include patient age (with premenopausal women being higher risk), grade III histology, and the presence of lymphovascular invasion or extracapsular nodal extension [26–29].

    • Breast Cancer: Stages I-II

      2015, Clinical Radiation Oncology
    • Breast Cancer: Stages I and II

      2012, Clinical Radiation Oncology: Third Edition
    View all citing articles on Scopus
    View full text