Intraoperative radiocolloid injection for sentinel node biopsy postneoadjuvant chemotherapy

Abstract Background This study sought to determine significance of radiocolloid injection timing for sentinel node biopsy (SNB) after neoadjuvant chemotherapy (NAC). Material and methods A retrospective comparison of intraoperative (IRCI) and preoperative (PRCI) radiocolloid injection for SNB was performed in breast cancer patients who had completed NAC. The sentinel node identification rate (SNIDR) was tested for noninferiority by a two-proportion z -test. The differences between clinical demographics, pathologic demographics, and SNIDR were evaluated by Fisher exact test. The difference in the number of sentinel nodes removed was analyzed by two-sample t -test. Results In the 6-y study period, 120 SNB were performed after NAC: 84 received PRCI and 36 received IRCI. The two groups were similar except there were fewer clinical T2 and more clinical T3 and T4 with IRCI ( P = 0.0008). The SNIDR was 92.9% with PRCI and 80.6% with IRCI. By two-proportion z -test, IRCI was not “noninferior” ( P = 0.5179). By Fisher exact test, the SNIDR of the two groups did not differ. The SNIDR differs only in patients who experience T downstaging (100% versus 80%, P = 0.0173). The mean number of lymph nodes removed was higher with IRCI: 3.38 versus 2.49 nodes ( P = 0.0068). There were more positive SNB with IRCI: 32.1% versus 55.2%, ( P = 0.0432). The incidence of nontherapeutic axillary dissection was similar between the two groups (3.6% for PRCI versus 5.6% for IRCI). Conclusions IRCI for SNB after NAC may be inferior to PRCI.