Surgical management of the breast and axilla after neoadjuvant treatment: the role of sentinel node biopsy

Several unique surgical issues arise in the management of patients who are selected to receive neoadjuvant systemic therapy. These involve the original diagnostic assessment of the extent of disease in the breast and axilla, the preoperative planning, and ultimately the surgical management of the primary breast tumor and that of axillary lymph nodes. Careful consideration of these issues is critical in order to maximize local control of the disease, while minimizing the extent of the required surgical resection and the ensuing surgical morbidity. Adequate diagnostic assessment with core needle biopsy before initiation of neoadjuvant systemic therapy ensures the presence of invasive carcinoma and provides adequate material for routine biomarker evaluation (such as ER, PR and HER-2 neu), while minimally disturbing the primary breast tumor. Consideration should also be given to assessing the status of axillary nodes by minimally invasive techniques such as ultrasound of the axilla with fine needle aspiration of suspicious nodes. Optimal preoperative planning aims at accurately determining the patterns of primary tumor shrinkage and the amount and location of any residual disease in the breast. Surgical treatment after neoadjuvant systemic therapy focuses on the management of the primary breast tumor and that of axillary lymph nodes. Regarding the primary breast tumor, several studies have shown that neoadjuvant systemic therapy converts a proportion of mastectomy candidates to candidates for breast-conserving surgery. Neoadjuvant systemic therapy can also decrease the amount of breast tissue that needs to be removed at lumpectomy even in patients who are lumpectomy candidates at presentation. Neoadjuvant systemic therapy (primarily neoadjuvant chemotherapy) downstages axillary lymph nodes in up to 30 to 40% of the patients. Although this observation was of little clinical significance when axillary node dissection was the sole method for staging the axilla, the development and validation of sentinel lymph node biopsy (SNB) has provided an additional potential advantage for neoadjuvant chemotherapy; that is, the possibility of decreasing the extent and morbidity of axillary surgery. This approach is, naturally, predicated on the premise that SNB is feasible and accurate following neoadjuvant chemotherapy. Initially, small, single-institution studies examined the efficacy of lymphatic mapping and the accuracy of SNB after neoadjuvant chemotherapy with significant variability in the rate of SN identification and in the rate of false negative SN [1]. However, when these studies are examined collectively [1,2] or when larger, multicenter datasets are analyzed [3], SNB after neoadjuvant chemotherapy appears to have similar performance characteristics to those of SNB before systemic therapy [4-6]. Some have proposed that candidates for neoadjuvant systemic therapy should have SNB before, rather than after, neoadjuvant systemic therapy so that information on the status of the axillary nodes be obtained without the potential confounding effects of systemic treatment, and sentinel node-negative patients can avoid axillary dissection [7-9]. Although this approach may be useful in patients who will not need systemic therapy (that is, chemotherapy) if the SN is negative, it is not generally useful for the majority of candidates for neoadjuvant systemic therapy, for whom little – if any – is to be gained by knowing the pathologic nodal status upfront. In addition, this approach commits patients to two surgical procedures and does not take advantage of the downstaging effect of neoadjuvant chemotherapy on the axillary nodes.