Author: By Lynda Williams, Senior medwireNews Reporter
medwireNews: The RISAS targeted approach to axillary dissection might help reduce the risk of missing residual disease while avoiding axillary lymph node dissection (ALND) in node-positive patients, suggests research presented during the 2020 San Antonio Breast Cancer Symposium.
The RISAS trial did not achieve the false-negative rate (FNR) for residual disease after neoadjuvant chemotherapy that was required to meet non-inferiority to ALND, reported presenting author Janine Simons, from the Erasmus Medical Center Cancer Institute in Rotterdam, the Netherlands.
Nevertheless, she described the study’s FNR of 3.47% as being “excellent”, confirming previous studies of targeted axillary dissection, which indicated better FNR rates with this approach than for sentinel lymph node biopsy (SLNB) or marking the axillary lymph node with radioactive iodine seeds (MARI).
This translated to residual disease being missed in one in 16 patients with a negative RISAS procedure compared with a one in six risk for the SLNB and MARI patients, the presenter explained.
For the study, 227 breast cancer patients underwent insertion of a radioactive iodine seed in their pathologically proven positive LN before neoadjuvant chemotherapy. The patients subsequently underwent surgery to remove the marked LN and all sentinel LNs, followed by completion ALND.
Overall, 98% of the patients had at least one LN identified and completed the RISAS procedure, 79 (35.4%) of whom achieved an axillary complete pathological response (pCR). Seventy-three of these pCR patients completed ALND, as did 135 of the 144 patients who had residual axillary disease.
Janine Simons reported that there were five false-negative results in five different institutions in the study, with four of these reports occurring within the first 10 procedures of each institution.
Residual disease in the ALND showed micrometastases in two nodes of one patient, and four patients had macrometastases in one (n=3) or two nodes.
This gave a FNR of 3.47% (5/144) with a 95% confidence interval of 1.38 to 7.16 – which exceeded the prespecified 6.24% upper bound of the non-inferiority margin – and a negative predictive value (NPV) of 93.59%.
“We conclude that the RISAS procedure, or a targeted axillary dissection, is the most suitable staging procedure for clinically node positive breast cancer treated with neoadjuvant chemotherapy because the chance to miss residual disease is the lowest with this procedure”, summarised Janine Simons.
“However, this study was only on the accuracy of targeted axillary dissection and we are still awaiting the results of ongoing trials that assess oncologic safety of de-escalation in this era”, she concluded.
Abstract GS1-10. Simons J, v Nijnatten TJA, Koppert LB, et al. Radioactive iodine seed placement in the axilla with sentinel lymph node biopsy after neoadjuvant chemotherapy in breast cancer: Results of the prospective multicenter RISAS trial. 2020 San Antonio Breast Cancer Symposium; 8–11 December.
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