Evaluation of Sentinel Lymph Node Biopsy After Primary Chemotherapy as Part of De-Escalation of Breast Cancer Treatment

Background: Sentinel lymph node biopsy (SLNB) after primary chemotherapy for node-positive breast cancer patients has been gaining popularity as part of the de-escalation of treatment. Aim: The 1ry aim was to assess the surgical outcome of node-positive patients who received primary chemotherapy followed by SLNB. A 2ry aim was to determine the rate of sentinel lymph node identification using the patent blue dye only technique. Methods: A prospective study that included 86 patients with invasive breast cancer and axillary lymph nodes metastasis as proved by ultrasound scan guided core biopsy. Following the completion of primary chemotherapy, sentinel lymph node biopsy was carried out for all patients at the time of breast surgery using the patent blue dye technique. Patients with negative SLNB underwent no further axillary procedure. Completion of axillary lymph node clearance was performed for positive SLNB patients. Results: The sentinel lymph node identification rate using the patent blue dye directed technique was 79%. Sixtyseven (78%) patients underwent wide local excision, and 35% did not need completion of axillary lymph node clearance due to downstaging following primary chemotherapy. Conclusions: Sentinel lymph node biopsy following primary chemotherapy for invasive breast cancer appears to be a safe, reliable technique, with an acceptable identification rate, even when using the patent blue dye technique only.


Introduction
Breast cancer (BC) is the second most common cancer after lung cancer and the most common cancer in women. It is one of the leading causes of death in females and its incidence, mortality, and survival rates vary considerably among different parts of the world, but in general, on the rise 1 .
It is well accepted that different types of breast cancer respond to different treatment modalities differently depending on tumor biology 2 . Following the establishment of the sentinel lymph node biopsy (SLNB) technique to assess nodal involvement in patients with invasive disease, axillary lymph node clearance (ALNC) became less popular. Axillary lymph node clearance is now only indicated in patients with macrometastasis if they do not have primary chemotherapy, as well as in patients with isolated tumor cells, micrometastasis, or macrometastasis after primary chemotherapy 3 .
Primary chemotherapy has become more popular, especially for triple negative, high-grade, and larger breast cancers as a tool to decrease tumor size, with the aim of breast conservation surgery (BCS) with better outcome 4 . Since primary chemotherapy has been associated with a good axillary nodal response, it is preferable to assess the nodal status after chemotherapy to avoid possible complications and morbidity following ALNC 5 .
The primary aim of this study was to assess the outcome of post-primary chemotherapy sentinel lymph node biopsy, and the secondary aim was to look into our sentinel lymph node identification rate using patent blue dye only technique.

Methods
This prospective study was conducted at the General Surgery Department, Fayoum University Hospital, Fayoum, Egypt from September 2016 to September 2019.

Patients
The study included adult (>18 years) women with invasive breast cancer and axillary lymph node involvement determined by ultrasound-guided core biopsy who received primary chemotherapy. Exclusion criteria included male gender, inflammatory breast cancer, local recurrence, previous ipsilateral axillary surgery, metastatic disease and non-completion of primary chemotherapy or no response to it.

Management plan
Initially, all patients underwent a triple evaluation, including clinical breast examination, imaging, and histopathological examination. Imaging included a digital mammogram and a bilateral breast and axillary ultrasound scan, with magnetic resonance imaging performed for a selected group of patients and a staging CT scan performed for all patients. Breast and axilla ultrasound scan was performed before starting primary chemotherapy, after three cycles, and after six cycles to assess the response and help in surgical planning. Some of the lobular cancers or patients with increased breast density on mammogram had breast magnetic resonance imaging as well.
All patients received four cycles of doxorubicin and cyclophosphamide followed by four cycles of paclitaxel. Patients with HER-2 positive disease received four doses of trastuzumab concurrent with paclitaxel, then Herceptin was continued after surgery for one year in total. Pathological complete response (pCR) is defined as the absence of residual invasive cancer on Hematoxylin and Eosin histological evaluation of the breast specimen and sampled axillary lymph nodes following primary systemic therapy.
Sentinel lymph node biopsy was performed for all patients at the time of breast surgery after injecting 2 ml of patent blue into the periareolar region at 10 o'clock. All blue-stained lymph nodes (sentinel lymph nodes) and non-blue palpable (nonsentinel lymph nodes) were harvested. A level one four-node sampling of palpable lymph nodes was performed when we were unable to identify the sentinel lymph node. The harvested nodes were sectioned into 24 sections, and we classified metastatic foci smaller than 0.2 mm as isolated tumor cells (ITC), foci measuring 0.2 -2 mm as micrometastasis, and foci larger than 2 mm as macrometastasis.
Patients were classified into two groups: group A, included patients who had negative SLNB, requiring no further axillary procedures, and group B, including patients with positive SLNB (i.e., isolated tumor cells, micrometastasis as well as macrometastasis), requiring completion axillary lymph node clearance. We assessed immediate complications up to 30 days postoperatively and delayed complications up to one year postoperatively and graded them according to the Clavien-Dindo system 6 .

Statistical methods
The collected data was organized and statistically analyzed using IBM SPSS software, version 22.0. (Armonk, NY: IBM Corp). Quantitative data were presented as mean and standard deviation. Qualitative data were presented as numbers and percentages.

Results
Eighty-nine patients were included in the study, of which 3 patients were excluded from the analysis (2 patients did not respond to 1 ry chemotherapy and 1 patient did not tolerate it). The mean (SD) age of the 86 patients included in the analysis was 58 (12.7) years and they were followed up for a mean of 16.8 months (SD, 4.3). Eighty-four (97.6%) of these patients presented palpable breast lesions, while 2 (2.4%) had nonpalpable breast lesions with involved axillary lymph nodes detected on screening mammograms.
Tumor characteristics are illustrated in Table 1. Most of the cancers were found in the upper outer quadrant, and the mean pre-chemotherapy ultrasound scan tumour size was 34 mm (SD 8). The final histology revealed that most cancers were invasive ductal carcinoma positive for oestrogen and progesterone receptors and 17 (19.8%) patients had diseases positive for human epidermal growth factor receptor-2 (HER-2). Fifty-four (62.8%) patients had a Ki67 level <14% and 32 (37.2%) patients had a Ki67 level <14%.

Mean (SD)
Tumor size pre-chemotherapy (mm) 34 (8) The outline of the management of the included 86 patients is shown in Figure 1.
All patients treated with wide local excision received adjuvant whole breast radiotherapy and some of those who underwent a mastectomy received chest wall radiotherapy.
Fifty-eight (67.4%) patients started adjuvant endocrine treatment (selective estrogen receptor modulators or aromatase inhibitors) for five years with the possibility of extension to ten years in the indicated patients, and 17 (19.8%) continued trastuzumab for a one-year period in total. The treatment modalities delivered are summarized in Table 2. While Group A patients who had only SLNB with negative lymph nodes did not report any immediate or delayed postoperative complications, Group B patients who underwent ALNC had immediate complications, including seroma (1/56, 1.8%) and minor wound infection (1/56, 1.8%). Delayed complications included persistent altered sensation at the medial aspect of the arm in 15 (26.8%) and mild lymphoedema in 4 (7.1%). None of the patients had limited arm motion. The mean hospital stay was two days.

Discussion
Axillary lymph node status does not only direct breast cancer treatment modalities but also plays a vital role in staging and predicting breast cancer prognosis. Hence, axillary lymph node clearance has traditionally been an essential part of the breast cancer management 7 .
Sentinel lymph node biopsy has recently been considered the standard procedure for axillary lymph node histological assessment in clinically node-negative breast cancer and since its introduction, the number of axillary lymph node clearance has significantly decreased 8 .
Recent advances in multimodal treatment have improved breast cancer outcomes and led to a decrease in the magnitude of breast surgery and an increase in the number of breast preservation surgeries after primary chemotherapy, and reduced the number of patients who require axillary clearance. Several studies have confirmed that SLNB after primary chemotherapy may be a feasible and acceptable option to avoid unnecessary axillary dissection 9 .
Unfortunately, traditional imaging and magnetic resonance imaging are not accurate in assessing axillary nodal status after primary chemotherapy 10 . Fowler et al. recommended a combined anatomical and functional/molecular imaging approach as the most accurate method to assess post-primary chemotherapy axillary nodal status 11 .
Post-chemotherapy SLNB is an acceptable and reliable tool to assess the axilla and obtain relative histological findings. It is well known that micrometastasis and isolated tumor cells found after primary SLNB without primary chemotherapy are not considered metastatic disease, as their presence does not affect survival. In contrast, their presence in SLNB after primary chemotherapy is regarded as a residual metastatic disease 12 .
In our cohort, 67 (19.5%) lymph nodes were tumor-free, 96 (28%) had pCR with treatment changes, 38 (11.1%) had ITC, 45 (13.1%) had micrometastases, and 97 (28.3%) had macrometastases. There is always a risk of false negative rate with SLNB after chemotherapy which can be attributed to anatomical alterations, interruption or blocking of lymphatic drainage by chemotherapy due to inflammation or fibrosis 13 . Enokido et al. reported a sentinel lymph node identification rate of 89.6% with a false negative rate of 14.2% after primary chemotherapy 14 . Our sentinel lymph node identification rate was 79.1%.
In the GANEA-2 study, after a 36-month followup, only one patient (0.2%) of 419 patients had an axillary recurrence, with a false negative rate of 11.9% 15 . The number of sentinel lymph nodes harvested was found to be associated with a decrease in the false negative rate, which was reported to be 7.3% in the Sentinel Neoadjuvant (SENTINA) study and 9.1% in the American College of Surgeons Oncology Group (ACOSOG) Z1071 trial when three or more sentinel lymph nodes were retrieved 16 . Mean number of sentinel lymph nodes harvested per patient in our cohort was 2.3 lymph node (196/86) Rouzier et al. suggested that the axillary nodal status after primary chemotherapy reflects the prognosis more accurately than the initial nodal status 17 . Therefore, axillary lymph node clearance might not be necessary for patients with a complete pathologic response 18 .
Sentinel lymph node biopsy after primary chemotherapy was found to help identify previously positive axillary lymph nodes to a negative status, hence avoiding axillary lymph node clearance leading to reduced arm motion morbidity and lymphedema 16 . In our cohort, 30 (34.9%) patients did not need axillary clearance due to negative sentinel lymph nodes following primary chemotherapy. After one year, our total arm lymphedema rate was 8.1% (7/86) and persistent altered sensation at the medial aspect of the arm was observed in 13 (15.1%) (13/86).
The complete axillary pathological response rate was 35% in the current study. Choi et al. achieved complete pathologic response of the axillary in 51.9% of the patients after primary chemotherapy 19 , and Shen J et al. achieved complete pathologic response in the axilla in 30% of their patients after neoadjuvant chemotherapy. They recommended axillary lymph node clearance for patients with biopsy-determined node metastases regardless of response to neoadjuvant treatment 20 . It is prudent to note that hormone negative status, HER-2 positive disease, and absence of lymphovascular invasion have been associated with a more complete axillary pathologic response 10 .
Despite all available evidence, some authors still insist that omission of axillary lymph node clearance requires identifying at least three sentinel lymph nodes with complete pathological response 21 .

Limitations
Only 86 patients were included in our analysis, with a short follow-up time. Therefore, a study with longer follow-up and a larger sample size is needed to be able to assess the recurrence rate and survival.
Unfortunately, we did not have the recourses for radioactive directed SLNB. This is the reason why we used the patent blue directed technique.

Conclusions
Sentinel lymph node biopsy following primary chemotherapy for invasive breast cancer disease appears to be a safe reliable technique, with a good identification rate even when using patent blue dye technique only. Further studies with a larger sample size and longer follow-up comparing patent blue dye technique to dual technique will provide more information to achieve the optimum outcome.
neoadjuvant chemotherapy for breast cancer in two