Significance of axillary lymph node extranodal soft tissue extension and indications for postmastectomy irradiation

BACKGROUND Extranodal soft tissue extension of axillary lymph node metastases (ETE) has been considered an indication for postmastectomy radiotherapy, including the axilla. However, it is unclear whether patients with ETE are at an increased risk of axillary recurrence. METHODS From a single institutional database of 2362 patients with breast carcinoma treated between 1974–1994, a total of 487 patients who underwent mastectomy for lymph node positive, infiltrating (T1‐T3) breast carcinoma was found. All the patients had pathologically confirmed axillary lymph node metastases and negative surgical margins; none had received postoperative irradiation. Of these patients, 50 had histologically documented axillary ETE. Forty‐three patients had a minimum follow‐up of at least 1 year and comprise the study population. The median follow‐up time of surviving ETE positive patients was 79 months. Twenty‐five patients (58.1%) received adjuvant systemic therapy. Sites of first failure were local or distant. Local failure was categorized further as chest wall failure, axillary failure, supraclavicular lymph node failure, or internal mammary lymph node failure. RESULTS For the 43 patients with ETE, the median patient age was 59.5 years (range, 38–81 years) and the median tumor size was 3.6 cm (range, 0.5–12.0 cm). The median number of positive axillary lymph nodes was 6 (range, 1–36 lymph nodes) versus 2 (range, 1–30 lymph nodes) for all T1‐T3 ETE positive patients compared with ETE negative patients (P < 0.001). The risk of ETE increased significantly with increasing numbers of axillary lymph node metastases (P < 0.001). Of the patients with ETE, 16 (37.2%) developed recurrent disease. ETE positive patients with disease recurrence had significantly greater numbers of positive axillary lymph nodes (median, 10 lymph nodes) than those patients who were recurrence free (median, 4 lymph nodes) (P = 0.02). The site of first failure was local in 7 patients (16.3%) and distant in 9 patients (20.9%). All patients with local recurrence had chest wall failures; there were no isolated lymph node recurrences. The only simultaneous local and distant failure was in one patient presenting with supraclavicular and intraabdominal metastases. CONCLUSIONS The risk of axillary recurrence, either as an isolated event or as part of simultaneous failure, is extremely low, even in patients with ETE. These data suggest that patients with ETE frequently have higher numbers of positive axillary ly