P3-07-47: Validated Nomogram To Predict Sentinel Lymph Node Positivity in Breast Cancer Patients.

Abstract

Abstract Background: Sentinel lymph node(SLN) biopsy is commonly used to assess axillary lymph node status in breast cancer patients. Intraoperative (frozen section) evaluation of SLN may lead to immediate axillary dissection if the lymph node is found to be positive. In light of the recent outcomes of the Z00011 trial, the use of intraoperative evaluation for SLN should diminish since only select patients appear to benefit from axillary dissection. We have previously reported that tumor size and lymphovascular invasion (LVI) strongly predict SLN positivity in a cohort of 350 breast cancer patients [Modern Pathology (2011) 24, 30A]. From this test cohort, we developed a nomogram which could help identify patients more likely to have sentinel lymph node positivity. The aim of this study was to validate the efficacy of this nomogram by applying a new, non-overlapping cohort of breast cancer patients who had undergone sentinel lymph node sampling. Materials and Methods: 93 breast cancer patients aged 29–82 (mean:59) who underwent excision (54, 58%) or mastectomy (39, 42%) with a SLN biopsy were studied. Patients who had undergone neoadjuvant chemotherapy were excluded. Clinicopathologic parameters such as number of sentinel lymph nodes removed and/or positive, number of non-sentinel lymph nodes removed and/or positive, tumor size, histologic type/grade, presence of lymphovascular invasion, biomarker expression (ER,PR, HER-2/neu) and multifocality were recorded. Statistical analysis was performed to identify which variables correlated with SLN positivity in this validation cohort. In addition, the probability of SLN positivity for each case was determined by using the nomogram and this value was then compared to the patient's true SLN status. Results: When analyzed separately, tumor size (p=0.03) and LVI (p=0.01) were variables that were significantly associated with SLN positivity in both the test and validation cohorts. Employment of the nomogram demonstrated that 60% of patients who were predicted to have a positive SLN with at least 0.8 probability were truly positive by histologic and immunohistochemical examination. Moreover, 89% of patients who were predicted to have a negative SLN with at least 0.8 probability were truly negative by histologic and immunohistochemical examination. Conclusions: We conclude that the utility of this nomogram prior to surgery can help predict SLN positivity. This can serve as a complimentary adjunctive tool to better select patients who will likely need intraoperative evaluation of their sentinel lymph node due to their higher risk of sentinel node positivity and thus, benefit from the option of immediate axillary dissection at that time. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P3-07-47.