Background: This study was performed to investigate the extent of tumor downstaging achieved in women with operable breast cancer treated with neoadjuvant chemotherapy and breast-conservation surgery, develop recommendations for effective surgical planning, and report local-regional recurrence rates with this approach.

Methods: One hundred nine patients with stage II or III (T3N1) breast cancer were treated in three prospective trials utilizing four cycles of 5-fluorouracil, doxorubicin, and cyclophosphamide (FAC, n = 72) or paclitaxel (n = 37) followed by segmental resection (n = 109) and axillary node dissection (n = 94). Postoperatively, patients received 4 additional cycles of FAC followed by irradiation of the breast. The median follow-up was 53 months.

Results: The median tumor size was 4 cm (range 1.1 to 9 cm) at presentation and only 1 cm (range 0 to 4.5 cm) after four cycles of chemotherapy. The primary tumor could not be palpated after chemotherapy in 55% of 104 patients presenting with a palpable mass and therefore required needle localization or ultrasound guidance for surgical resection. Of the 34 patients clinically deemed to have no residual carcinoma in the breast after chemotherapy and before surgery, only 50% of these patients were found to have no residual carcinoma on pathologic examination after surgery. Patients with primary tumors ≤2 cm were significantly more likely than patients with larger tumors to have complete eradication of the primary tumor prior to surgery (P <0.001). The 5-year local-regional recurrence rate was 5%.

Conclusions: Tumor downstaging is marked in patients with operable breast cancer and requires close monitoring during chemotherapy. We recommend placement of metallic tumor markers when the primary tumor is ≤2 cm to facilitate adequate resection and pathologic processing. Resection of the tumor bed remains necessary in women deemed to have a complete clinical response to ensure low rates of recurrence.