Quantitative intra-operative RT-PCR assay predicts size of sentinel node metastases.

Abstract

Abstract Abstract #1002 The GeneSearch™ Breast Lymph Node (BLN) Assay (Veridex, LLC) has been FDA approved to detect metastases > 0.2 mm in the sentinel lymph nodes (SLNs) of breast cancer patients and has been in clinical use in our institute for 11 months. This assay gives a qualitative (negative/positive) result by applying cutoff values to the cycle times (Ct) of the two mRNA markers analyzed: mammaglobin (MG) (cutoff value = 31 Cts) and cytokeratin 19 (CK19) (cutoff value = 30 Cts). This is the first study to evaluate if the quantitative Ct values of MG and CK19 can be used to estimate probable size of nodal metastases.
 To date 184 patients have been tested using the BLN Assay during its clinical use at Morton Plant Hospital. An additional 172 patients were tested with the BLN Assay at our institute during investigational studies. In both cases, the SLNs of breast cancer patients were divided into ∼2 mm pieces. Alternating pieces were homogenized and were processed intra-operatively. The other pieces of the SLN were used for permanent section H&E analysis. The patient was considered H&E positive when a metastasis > 0.2 mm was identified. During clinical use, same-surgery complete axillary dissection was performed when the assay was positive (n = 34).
 Performance of the assay's qualitative result against permanent section H&E on adjacent node pieces was similar for the two groups (total N = 356), for a total sensitivity of 96% (81/84), specificity of 93% (254/272), and overall agreement of 94%. The marker Ct values correlated with metastases size as determined by H&E in adjacent node pieces (r = 0.74 for MG and 0.72 for CK19, p < .0001). The lower the Ct values, the greater the likelihood of macrometastases reported by H&E, as described in Table 1. For example if CK19 is <21.0 and MG is < 25.0, there is 100% chance for H&E positivity in the SLNs, with the majority being macrometastases.
 
 Additionally, BLN Assay Ct values in the SLN were predictive of metastases in the non-SLN nodes. For example, of the 12 patients who had a SLN with CK19 < 24 Cts, 9 (75%) had H&E positive non-SLNs. For the same 12 patients, SLNs were H&E positive (5 macrometastases, 5 micrometastases, and 2 reported as > 0.2 mm).
 The BLN Assay's high intra-operative qualitative performance minimizes the need for second surgeries for complete axillary dissections. Results from this investigational study examining the marker Ct values suggest that the assay may provide valuable individual tumor volume data intra-operatively or post-operatively. Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 1002.