The impact of axillary lymph node metastasis density determined by pre-treatment pet on the selection of axillary surgical method in breast cancer patients after receiving neoadjuvant therapy

INTRODUCTION: Neoadjuvant chemotherapy is an accepted treatment for locally advanced breast cancer, inflammatory breast cancer, and biologically aggressive breast cancer. Additionally, it is a suitable approach for patients with ipsilateral lymph node metastasis and those seeking breast-conserving surgery with operable breast cancer. The surgical treatment of breast cancer consists of breast-conserving surgery (BCS) and mastectomy. BCS is the standard approach in early-stage breast cancer surgery. In the context of axillary surgery, sentinel lymph node biopsy (SLNB) and axillary lymph node dissection (ALND) are included. SLNB is routinely performed in breast cancer patients with clinically and radiologically axilla-negative findings. In certain situations, SLNB can also be performed in cases such as T3 tumors, after neoadjuvant chemotherapy (NAC), and in pregnant patients. AİM: The management of the axilla after neoadjuvant chemotherapy (NAC) in breast cancer patients with axillary lymph node metastasis is still a subject of debate. The aim is to investigate factors that can guide the determination of the most appropriate axillary surgical method based on metastasis density, by analyzing pre-treatment PET determined axillary lymph node metastasis density, post-treatment PET results, and postoperative histopathological findings. The aim is to identify criteria that should be followed to perform less invasive sentinel lymph node biopsy (SLNB) in patients who achieve a complete axillary response after neoadjuvant chemotherapy (NAC), based on PET results, in order to reduce the morbidity of axillary lymph node dissection (ALND). MATERIALS AND METHODS: In this study, the clinical data of patients who were diagnosed with breast cancer, and received neoadjuvant chemotherapy followed by surgery in General Surgery Clinic of Istanbul University-Cerrahpaşa between 2016 and 2022 were evaluated. Radiological and pathological parameters, before and after neoadjuvant chemotherapy were determined as independent groups and compared in terms of axillary lymph node response in the post-neoadjuvant chemotherapy period. Clinical data included age, tumor histopathological type, tumor grade, localization of axillary lymph nodes, number of lymph nodes and level of lymph node response to neoadjuvant chemotherapy, all evaluated retrospectively. RESULTS: In patients with HER2-negative status, the rate of pathological complete response was found to be higher compared to those with HER2-positive status. Patients who achieved a partial response after neoadjuvant therapy (NAK), the average Ki-67 index (33.8) was found to be higher compared to those who achieved a complete response (29.8) (p=0.037). In patients with a complete response, the rate of calcification in histopathological examination was found to be higher compared to those with a partial response (p=0.004). The accuracy rate of PET imaging was determined to be 88.6%. Sensitivity 75.6%, specificity 100%, positive predictive value 100%, and negative predictive value was 82.4%. A statistically significant relationship was found between the number of metastatic axillary lymph nodes identified by PET before NAK and the postoperative pathological response (p=0.034). In patients with one positive lymph node, the rate of complete response was found to be higher compared to patients with two or more positive lymph nodes. CONCLUSİON: There are different imaging methods available for the accurate assessment of response after treatment in breast cancer patients receiving neoadjuvant therapy. PET-CT imaging is an important diagnostic tool in evaluating axillary response. The accuracy rate has been calculated as 100% in patients showing partial response and 82.4% in those showing complete response. In PET-CT imaging, axillary dissection is considered an appropriate method in patients showing partial response. In patients showing complete response, sentinel lymph node biopsy may be performed regardless of the pre-treatment lymph node involvement intensity.