Implication of intraoperative sentinel node imprint cytology for consent in the SNAC Trial.

Background: Women randomized into the sentinel node biopsy-only arm of the Sentinel Node versus Axillary Clearance Trial require axillary clearance if the sentinel node is unable to be identified, or if the sentinel node contains metastases. The aim of the present study was to determine the likelihood of immediate and delayed axillary clearance in patients in the trial when nodes were subjected to intraoperative imprint cytology.

Methods: A prospective database for 400 patients with operable breast cancer was analysed to determine the likelihood of lymph node involvement according to tumour size. The ability to successfully remove a sentinel node and the accuracy of intraoperative imprint cytology of sentinel nodes was investigated. These data were used to predict the likelihood of patients proceeding to immediate or delayed axillary clearance.

Results: The rate of lymph node involvement was 0%, 10%, 30%, and 53% in tumours measuring <5 mm, 6-10 mm, 11-20 mm and 21-30 mm, respectively. A sentinel node was identified in 95% of cases. In a series of 79 consecutive cases using intraoperative imprint cytology, 37% of sentinel nodes containing metastases were identified intraoperatively. The estimated likelihood of undergoing immediate axillary clearance therefore ranges from 5% for tumours <5 mm, up to 24% for tumours 21-30 mm. Similarly the likelihood of delayed clearance ranges from 0% to 32% depending on tumour size.

Conclusions: It is possible to give detailed and accurate information to patients undergoing sentinel node biopsy about both the risk of lymph node involvement and the likelihood of requiring immediate or secondary axillary clearance.