Factors associated with regional nodal failure in patients with early stage breast cancer with 0-3 positive axillary nodes following tangential irradiation alone

Purpose: Recent randomized trials have suggested that improved local-regional control after radiation therapy significantly increases survival for breast cancer patients with positive axillary nodes treated with adjuvant systemic therapy . It has been our policy to use a third radiation field only in patients with 4 or more positive nodes. The purpose of this study was to assess whether there are any clinical or pathologic factors associated with an increased risk of regional nodal failure (RNF) in patients with 0-3 positive nodes treated with tangential radiotherapy (RT) alone with or without systemic therapy. Methods and Materials: We retrospectively analyzed the incidence of RNF for 691 patients with clinical Stage I or II invasive breast cancer treated with complete gross excision of the primary tumor and tangential RT alone between 1978-87; 12% also received systemic therapy. All had 0-3 positive nodes on axillary dissection that had histologic examination of ≥ 6 nodes, and all had potential 8-year follow-up. The median number of axillary nodes removed was 11 (range 6-36). RNF was defined as any recurrence in ipsilateral axillary, internal mammary, supraclavicular, or infraclavicular nodes in the absence of recurrence in the breast, with or without simultaneous distant metastasis. Crude rates for first sites of failure within the first 8 years after treatment were calculated. A polychotomous logistic regression was used to identify factors prognostic for RNF and other sites of first failure. Results: Within 8 years, RNF was the first site of failure for 27 patients for a crude 8-year rate of 3.9%. Isolated axillary failure occurred in 8 patients (1.2%). Isolated supraclavicular and/or infraclavicular failure occurred in 5 (1.3%) and 3 (0.4%) patients, respectively. Isolated internal mammary node failure occurred in 2 patients (0.3%). A polychotomous logistic regression model of first site of failure (local failure, regional nodal, distant/opposite breast, dead without recurrence, no evidence of disease) within 8 years found age <50 years, moderate or marked necrosis, size greater than 1 cm, and presence of an extensive intraductal component (EIC) to be significantly correlated with site of first failure, but only the last two were associated with a significantly larger relative risk of RNF versus being no evidence of disease at 8 years. The incidence of RNF was 0.7% for patients with tumors ≤ 1 cm compared to 5.7% among patients with larger tumors. Among patients with EIC-positive tumors the incidence of RNF was 7.6% compared to 3.1% among those whose tumors were EIC-negative. Conclusions: Although the incidence of RNF has been shown to be somewhat higher in patients with tumors measuring greater than 1 cm and those with an EIC, RNF is uncommon among all subsets of patients with negative or 1-3 positive lymph nodes treated with conservative surgery, axillary dissection, and only tangential RT fields. Therefore, giving only tangential RT (without a separate nodal field) appears generally acceptable for patients with 0-3 positive nodes