The purpose of this study was to describe regional nodal failure patterns in patients who had undergone mastectomy with axillary dissection to define subgroups of patients who might benefit from supplemental regional nodal radiation to the axilla or supraclavicular fossa/axillary apex.

The cohort consisted of 1031 patients treated with mastectomy (including a level I-II axillary dissection) and doxorubicin-based systemic therapy without radiation on five clinical trials at M.D. Anderson Cancer Center. Patient records, including pathology reports, were retrospectively reviewed. All regional recurrences (with or without distant metastasis) were recorded. Median follow-up was 116 months (range, 6-262 months).

Twenty-one patients recurred within the low-mid axilla (10-year actuarial rate 3%). Of these, 16 were isolated regional failures (no chest wall failure). The risk of failure in the low-mid axilla was not significantly higher for patients with increasing numbers of involved nodes, increasing percentage of involved nodes, larger nodal size or gross extranodal extension. Only 3 of 100 patients with <10 nodes examined recurred in the low-mid axilla. Seventy-seven patients had a recurrence in the supraclavicular fossa/axillary apex (10-year actuarial rate 8%). Forty-nine were isolated regional recurrences. Significant predictors of failures in this region included > or = 4 involved axillary lymph nodes, >20% involved axillary nodes, and the presence of gross extranodal extension (10-year actuarial rates 15%, 14%, and 19%, respectively, p < 0.0005). The extent of axillary dissection and the size of the largest involved node were not predictive of failure within the supraclavicular fossa/axillary apex.

These results suggest that failure in the level I-II axilla is an uncommon occurrence after modified radical mastectomy and chemotherapy. Therefore, supplemental radiotherapy to the dissected axilla is not warranted for most patients. However, patients with > or = 4 involved axillary lymph nodes, >20% involved axillary nodes, or gross extranodal extension are at increased risk of failure in the supraclavicular fossa/axillary apex and should receive radiation to undissected regions in addition to the chest wall.