"The sentinel node will not accurately reflect the other lymph nodes in less than one percent of patients, and it's clear that SNB will be both more accurate and less traumatic than the axillary node procedure for the vast majority of patients," Dr. Tafra said.
Furthermore, the study is finding evidence that the technique used to analyze the SNB tissue may be an important factor in the accuracy of the results. When 36 false-negative SNB specimens from 18 patients were examined with a molecular test called RT-PCR, tumor cells were detected in 61% of these nodes. RT-PCR amplifies the signal from the tumor so that detection of metastatic cells is much more sensitive than with H&E, the standard pathology test. Additionally, in this study, tissue for RT-PCR was sampled throughout the sentinel node. Pathologists usually are able to examine only a few central sections of each lymph node, especially with the large number of nodes from standard axillary dissection, Dr. Tafra explained.
Early data from this study reveal a statistically significant increase in disease-free survival for patients whose nodal biopsies were negative for cancer on both pathology tests, suggesting that the cancer really was confined to the breast, compared with those whose biopsies were negative with H&E but positive with the more sensitive RT-PCR test.
"Thus far we've done RT-PCR analysis for less than half the patients enrolled in the study, but we're optimistic that another 12 months of data will demonstrate that even very small amounts of disease detected only by molecular methods can have clinical significance," Dr. Tafra concluded.