Pathologic tumor response in the breast following neoadjuvant chemotherapy predicts axillary lymph node status

Neoadjuvant chemotherapy is becoming the standard of care for locally advanced breast cancer. This study was performed to determine whether pathologic primary tumor response to neoadjuvant chemotherapy might predict axillary lymph node status and so be used to identify patients in whom surgery could be effectively limited to biopsy of the previous primary tumor site without axillary dissection.

Between 1992 and 1996, 170 consecutive patients with locally advanced breast cancer were treated in a prospective trial with four preoperative cycles of 5-fluorouracil, doxorubicin, and cyclophosphamide. Disease was staged before initiation of preoperative chemotherapy and before surgery. Segmental resection with axillary lymph node dissection or modified radical mastectomy was performed first, followed by postoperative chemotherapy and radiation therapy of the breast (or chest wall) and regional lymphatics. Patient and tumor characteristics associated with complete versus incomplete pathologic primary tumor response to neoadjuvant chemotherapy and correlation between primary breast tumor pathologic response and axillary lymph node status found at surgery were analyzed.

Of 156 evaluable patients, 30 patients (19%) had primary breast tumors that were completely eliminated after induction chemotherapy based on histologic assessment. Nineteen of those 30 patients (63%) had negative axillary lymph nodes at dissection, compared with 13 patients (33%) of the 40 who had a near-complete pathologic primary tumor response (< or = 1 cm3 remaining) and only 15 patients (17%) of the 86 who had > 1 cm3 tumor remaining in the pathology specimen of the breast primary. Of the 22 patients with a complete pathologic response in the breast and a clinically negative axilla after induction chemotherapy, axillary dissection revealed positive lymph nodes in four. These four patients had only one or two positive lymph nodes.

Because initial clinical regression of primary tumor with neoadjuvant chemotherapy is considered an excellent prognostic indicator and because patients with locally advanced breast cancer routinely receive local and regional radiation treatment followed by additional chemotherapy, the role of breast and axillary surgery has been questioned. In this study, a complete pathologic response of the primary tumor to induction chemotherapy is highly predictive of negative axillary lymph node status. Therefore, axillary lymph node dissection may be omitted in certain subsets of patients who have a biopsy-proven complete pathologic response in the primary tumor and a clinical negative axillary examination. Further prospective, randomized investigation is needed to confirm this finding.