Objective: To evaluate the clinical value of GeneSearch(TM) BLN Assay as an intra-operative diagnostic method of sentinel lymph node (SLN) for breast cancer patients.
Methods: A total of 479 consecutive patients from six centers were involved in this prospective study. The SLNs were identified, dissected and then sectioned along the short axis into multiple blocks. The odd blocks were tested intra-operatively by the above-mentioned assay and the even blocks assessed post-operatively by histopathologic examination. The 4 - 6 µm thick stepwise sectioning permanent HE slides were prepared every 150 µm and one block yielded 6 slides. In addition, the even blocks of 136 patients were prepared for frozen section (FS) and all blocks of 156 patients evaluated intra-operatively by touch imprint cytology (TIC).
Results: In the node basis analysis, its accuracy, sensitivity, specificity, positive predict value (PPV) and negative predict value (NPV) were 93.0%, 85.6%, 94.6%, 76.6% and 96.9% respectively. Its sensitivity was similar to that of FS (84.9%, P = 0.885) and significantly higher than that of TIC (70.0%, P = 0.007). When assessing nodes with macro-metastases, its sensitivity was similar to that of FS (93.6% vs 95.6%, P = 0.558) and significantly higher than that of TIC (93.6% vs 80.9%, P = 0.011). When assessing nodes with micro-metastases, it had a higher sensitivity than that of FS (57.5% vs 44.4%, P = 0.356) and TIC (57.5% vs 30.8%, P = 0.094). In the patient basis analysis, the accuracy, sensitivity, specificity, PPV and NPV were 91.4%, 87.5%, 92.9%, 81.8% and 95.3% respectively. Its sensitivity was similar to that of FS (84.5%, P = 0.576) and significantly higher than that of TIC (75.0%, P = 0.049). After adjustment, it had the accuracy, sensitivity, specificity, PPV and NPV of 91.7%, 83.5%, 95.2%, 88.3% and 93.0% respectively. Its sensitivity was higher than that of FS (72.1%, P = 0.054) and significantly higher than that of TIC (66.7%, P = 0.011). The two had no significant difference in the sensitivity and specificity. After a learning curve of around 10 cases, it could be performed in a median time of around 35 min. The threshold cycle time values of MG and CK-19 were 36 and 31 respectively. The type of metastases could be estimated approximately according to the cycle time values. The cycle time values of MG under 33 indicated SLN macro-metastases and those of 33-36 denoted micro-metastases. The values of CK-19 under 29 indicated SLN macro-metastases and those of 29-31 denoted micro-metastases.
Conclusion: As an accurate and rapid intra-operative assay for breast sentinel lymph nodes, the GeneSearch(TM) BLN Assay may replace FS and TIC in general medical practice.