Performance of four published risk models to predict sentinel lymph-node involvement in Australian women with early breast cancer.

BACKGROUND: Sentinel lymph-node biopsy has reduced the need for extensive axillary surgery for staging. It still exposes women to associated morbidity. Risk models that use clinical and pathology information of the primary tumour to predict sentinel lymph-node metastasis may allow further improvements in care. This study assessed the performance of four published risk models for predicting sentinel lymph-node metastasis in Australian women with early breast cancer; including one model developed in an Australian population. METHODS: The Sentinel Node Biopsy Versus Axillary Clearance (SNAC) trial dataset was used to assess model discrimination by calculating the area under the receiver-operating-characteristic curve (AUC) and the false-negative rate for sentinel lymph-node metastasis using model-predicted risk cut-points of 10%, 20%, 30%, and calibration using Hosmer-Lemeshow tests and calibration plots. RESULTS: The sentinel node was positive in 248 of 982 (25.2%) women (158 macrometastasis, 90 micrometastasis). The AUCs of risk models ranged from 0.70 to 0.74 for prediction of any sentinel-node metastasis; 0.72 to 0.75 for macrometastasis. Calibration was poor for the three models developed outside of Australia (lack-of-fit statistics, P < 0.001). For women with a model-predicted risk of sentinel lymph-node metastasis ≤10%, observed risk was 0-13% (three models <10%), false-negative rate 0-9%; 1-17% of women were classified in this range. CONCLUSION: All four models showed good discrimination for predicting sentinel lymph-node metastasis, in particular for macrometastasis. With further development such risk models could have a role in the provision of reassurance to low risk women with normal nodes sonographicaally for whom no axillary surgery is contemplated.

Identification of the sentinel lymph node in the SNAC-1 trial.

BACKGROUND: A combination of scintigraphy and a lymphotropic dye (patent blue dye (BD)) is the recommended technique to detect the sentinel lymph node (SLN) in early breast cancer. This study determined the effect of clinical factors on SLN identification in the sentinel node biopsy versus axillary clearance (SNAC) trial. METHODS: A total of 1088 women were registered. Lymphatic mapping was performed using preoperative lymphoscintigraphy (LSG) and gamma probe (GP) combined with peritumoural injection of patent BD (971 patients) or BD alone (106 patients). RESULTS: SLNs were identified in 1024 women (94%), localized with LSG in 779 (81.4%), and were identified by GP in 879 (91.8%). The BD identified SLNs in 890 of 1073 (82%) women. Three patients had allergic reactions. BD detected the SLNs in 141 of 178 women with negative LSG mapping and in 44 of 79 women with no hot SLNs detected intraoperatively. Age, body mass index (BMI) and tumour presentation (screen detected versus symptomatic) were significantly related to the identification of the SLN. For BD, the primary tumour location was significantly related to identification rate. The detection of blue SLN was significantly lower in women with inner quadrant tumours. CONCLUSION: The combined technique resulted in a high identification rate. BD contributed to the identification of the SLNs in patients where LSG and GP failed to identify the sentinel node. Special attention to these techniques is needed in particular groups of patients such as those with high BMI, screen-detected primary tumours and tumour located in the inner quadrants.