Challenges to I-125 Seed Localization of Metastatic Axillary Lymph Nodes Following Neoadjuvant Chemotherapy

The objective of this retrospective study is to characterize challenges with ultrasound (US)-guided localization of clipped metastatic axillary lymph nodes after neoadjuvant chemotherapy.

After institutional review board approval, our radiology database was searched for all radioactive seed localizations (RSLs), which use a low-dose radioactive isotope, Iodine-125, performed for clipped axillary lymph nodes between January 1, 2016, and December 31, 2018. The details of each procedure were reviewed. RSL was defined to be successful if US-guidance was used, and postlocalization imaging showed the seed was no more than 1 cm away from the target. Cause and subsequent management of unsuccessful localizations were documented.

During the study period, 139 clipped axillary lymph nodes (in 138 women and 1 man) were scheduled for preoperative RSL. The overall success rate of RSL was 106/139 (76%). The number of unsuccessful localizations was 10/37 (27%) in 2016, 7/39 (18%) in 2017, and 16/63 (25%) in 2018, with a total unsuccessful case frequency of 33/139 (24%) over the entire study period. The mean time interval between marker placement and localization was 6.0 months (range 0.4-18.1 months). The coil biopsy marker was the most frequently used marker.

Preoperative US-guided I-125 seed localization of clipped metastatic axillary lymph nodes is suboptimal or unsuccessful 24% of the time. Other options for non-US imaging-guided localizations, such as tomosynthesis, are available for consideration when US detection is unsuccessful.