Axillary Management of Stage II/III Breast Cancer in Patients Treated with Neoadjuvant Systemic Therapy: Results of CALGB 40601 (HER2-Positive) and CALGB 40603 (Triple-Negative)

Systemic Therapy Advances for HER2-Positive and Triple Negative Breast Cancer: What the Surgeon Needs to Know

Neoadjuvant systemic therapy (NST) was initially reserved for unresectable patients however it has been increasingly used to facilitate breast conservation, downstage the axilla, and inform adjuvant therapy decisions based on response. For patients with HER2+ and triple-negative breast cancer (TNBC), clinical trials have resulted in the ability to individualize treatment regimens. For HER2+ breast cancer, de-escalation of neoadjuvant regimens to minimize cytotoxic chemotherapy and de-escalation or escalation of adjuvant regimens based on response have been effective. For TNBC, the approval of the combination of chemotherapy plus immunotherapy in the neoadjuvant setting has resulted in a major practice shift and opened the door to many additional treatment questions including de-escalation of the chemotherapy backbone or the adjuvant regimen. For both HER2+ and TNBC, most patients are treated with NST except those with very small tumors. Efforts are also being made to optimally identify patients with T1c tumors who may benefit from more aggressive NST. For patients treated according to or enrolled in NST de-escalation trials, breast conservation (even those who become eligible based on response to NST) and sentinel lymph node biopsy when cN0 at the completion of NST are safe and feasible. Continued involvement of surgeons and multidisciplinary teams in the design and reporting of trials will streamline their adoption into clinical practice. Surgeons need to remain aware of ongoing systemic therapy trials to appropriately select patients for NST and plan for appropriate post-neoadjuvant surgical care.

Axillary Nodal Response to Neoadjuvant T-DM1 Combined with Pertuzumab in a Prospective Phase II Multi-Institution Clinical Trial

BACKGROUND

Patients with ERBB2 (HER2)-positive breast cancer experience high pathologic complete response (pCR) rates after standard neoadjuvant anti-HER2 systemic therapy. We examined axillary pathologic nodal response to neoadjuvant dual HER2-targeted therapy alone, based on breast pathologic response, in a multi-institution clinical trial.

STUDY DESIGN

Patients with HER2-positive breast cancer were enrolled to a phase II single-arm trial, which administered 6 cycles of neoadjuvant trastuzumab emtansine (T-DM1) plus pertuzumab. Rates of pathologic nodal disease (ypN) in patients who were clinically node-negative (cN0) and node-positive (cN1) were analyzed, by residual breast disease (pCR and residual cancer burden [RCB] I to III).

RESULTS

One hundred fifty-eight patients completed preoperative treatment and proceeded to surgery. Of 92 patients who were cN0, 48 (52.2%) and 10 (10.9%) experienced breast pCR and RCB I, respectively. Of these, 100% were ypN0. Of 34 with RCB II to III, 26 (76.5%) were ypN0. Of 30 patients who were cN1 with breast pCR, 100% were ypN0; of the 12 patients who were cN1 with RCB I, 66.7% were ypN0; and of the 24 patients who were cN1 with RCB II to III, 25% were ypN0. ypN0 rates were significantly different between patients who did and did not experience a pCR, in both cN0 (p = 0.002) and cN1 (p < 0.001) subgroups.

CONCLUSIONS

Patients with HER2-positive breast cancer treated with dual HER2-targeted therapy who experienced a breast pCR or RCB I response were frequently ypN0. These findings support future trials considering omission of axillary surgical staging for patients with HER2-positive breast cancer in neoadjuvant trials of active HER2-targeted regimens, particularly if they experience breast pCR or RCB I.

Diagnostic Accuracy of Radioactive Iodine Seed Placement in the Axilla With Sentinel Lymph Node Biopsy After Neoadjuvant Chemotherapy in Node-Positive Breast Cancer

Importance

Several less-invasive staging procedures have been proposed to replace axillary lymph node dissection (ALND) after neoadjuvant chemotherapy (NAC) in patients with initially clinically node-positive (cN+) breast cancer, but these procedures may fail to detect residual disease. Owing to the lack of high-level evidence, it is not yet clear which procedure is most optimal to replace ALND.

Objective

To determine the diagnostic accuracy of radioactive iodine seed placement in the axilla with sentinel lymph node biopsy (RISAS), a targeted axillary dissection procedure.

Design, Setting, and Participants

This was a prospective, multicenter, noninferiority, diagnostic accuracy trial conducted from March 1, 2017, to December 31, 2019. Patients were included within 14 institutions (general, teaching, and academic) throughout the Netherlands. Patients with breast cancer clinical tumor categories 1 through 4 (cT1-4; tumor diameter <2 cm and up to >5 cm or extension to the chest wall or skin) and pathologically proven positive axillary lymph nodes (ie, clinical node categories cN1, metastases to movable ipsilateral level I and/or level II axillary nodes; cN2, metastases to fixed or matted ipsilateral level I and/or level II axillary nodes; cN3b, metastases to ipsilateral level I and/or level II axillary nodes with metastases to internal mammary nodes) who were treated with NAC were eligible for inclusion. Data were analyzed from July 2020 to December 2021.

Intervention

Pre-NAC, the marking of a pathologically confirmed positive axillary lymph node with radioactive iodine seed (MARI) procedure, was performed and after NAC, sentinel lymph node biopsy (SLNB) combined with excision of the marked lymph node (ie, RISAS procedure) was performed, followed by ALND.

Main Outcomes and Measures

The identification rate, false-negative rate (FNR), and negative predictive value (NPV) were calculated for all 3 procedures: RISAS, SLNB, and MARI. The noninferiority margin of the observed FNR was 6.25% for the RISAS procedure.

Results

A total of 212 patients (median [range] age, 52 [22-77] years) who had cN+ breast cancer underwent the RISAS procedure and ALND. The identification rate of the RISAS procedure was 98.2% (223 of 227). The identification rates of SLNB and MARI were 86.4% (197 of 228) and 94.1% (224 of 238), respectively. FNR of the RISAS procedure was 3.5% (5 of 144; 90% CI, 1.38-7.16), and NPV was 92.8% (64 of 69; 90% CI, 85.37-97.10), compared with an FNR of 17.9% (22 of 123; 90% CI, 12.4%-24.5%) and NPV of 72.8% (59 of 81; 90% CI, 63.5%-80.8%) for SLNB and an FNR of 7.0% (10 of 143; 90% CI, 3.8%-11.6%) and NPV of 86.3% (63 of 73; 90% CI, 77.9%-92.4%) for the MARI procedure. In a subgroup of 174 patients in whom SLNB and the MARI procedure were successful and ALND was performed, FNR of the RISAS procedure was 2.5% (3 of 118; 90% CI, 0.7%-6.4%), compared with 18.6% (22 of 118; 90% CI, 13.0%-25.5%) for SLNB (P < .001) and 6.8% (8 of 118; 90% CI, 3.4%-11.9%) for the MARI procedure (P = .03).

Conclusions and Relevance

Results of this diagnostic study suggest that the RISAS procedure was the most feasible and accurate less-invasive procedure for axillary staging after NAC in patients with cN+ breast cancer.

Meta-analysis of neoadjuvant therapy and its impact in facilitating breast conservation in operable breast cancer

Background

Neoadjuvant therapy (NAT) for operable breast cancer may facilitate more breast-conserving surgery (BCS). It seems, however, that this benefit is not being realized fully.

Methods

A systematic review of the literature was performed. RCTs were included. The criteria for inclusion were: documentation of surgical assessment before and after NAT, surgery performed (BCS or mastectomy), and clinical and pathological responses.

Results

A total of 1452 patients from seven RCTs met the inclusion criteria. After NAT, the feasibility of BCS increased from 43·3 to 60·4 per cent (P &lt; 0·001), but BCS was performed in only 51·8 per cent (P = 0·04). Only 31 per cent of patients who became eligible for BCS (assessed on clinical response) underwent BCS (pooled rate ratio 0·31, 95 per cent c.i. 0·22 to 0·44; P &lt; 0·001). Of the mastectomy candidates who achieved a pathological complete response after NAT, only 41 per cent underwent BCS (pooled rate ratio 0·41, 0·23 to 0·74; P = 0·003). The main factors that influenced the decision not to shift to BCS, even though it was feasible, were clinical assessment before NAT, multicentricity and tumour size at presentation.

Conclusion

Breast surgery performed after NAT does not reflect tumour response, resulting in potentially unnecessary radical surgery, especially mastectomy. The barriers to maximizing the surgical benefits of NAT need to be better understood and explored.

Processing and Reporting of Breast Specimens in the Neoadjuvant Setting

Standardization of quantification of residual disease in the breast and lymph nodes with routine pathologic macroscopic and microscopic evaluation leads to accurate and reproducible measures of response to neoadjuvant treatment. Multidisciplinary collaboration and correlation of clinical, imaging, gross and microscopic findings is essential. The processing approach to post-neoadjuvant breast cancer surgical specimens and the elements needed in the pathology report are the same regardless of breast cancer subtype or type of neoadjuvant treatment. The residual cancer burden incorporates response in the breast and in the lymph nodes into a score that can be combined with other emerging prognostic factors.