Significance of a positive sentinel lymph node biopsy in staging for distant metastasis in breast cancer: are current guidelines relevant?

In breast cancer, early identification of distant metastasis changes management. Current guidelines recommend radiological staging in patients with a preoperative positive axilla; no guidelines address a preoperative negative axilla with subsequent positive sentinel lymph node biopsy. This study investigates whether current guidelines adequately identify distant metastasis in a positive sentinel lymph node biopsy population that had radiological staging.

Patients diagnosed with primary breast cancer between 1 January 2013 and 1 October 2017 with a positive sentinel lymph node biopsy and subsequent radiological staging from a single unit were included. A systematic search identified relevant guideline criteria, against which patients were audited.

A total of 330 patients with positive sentinel lymph node biopsy were identified; 227 (69%) had radiological staging postoperatively with computed tomography (5.3%), bone scan (2.6%) and both (92%) which identified 8/227 (3.5%) patients had distant metastasis. Patients with distant metastasis (DMp) compared with those without distant metastasis (NDMp) were associated with poorly differentiated tumours (DMp 62% vs NDMp 28%; p = 0.037), high-grade ductal carcinoma in situ (DMp 75% vs NDMp 39%; p = 0.043) and increased mean invasive tumour size (DMp 37mm vs NDMp 24mm; p = 0.014). Binomial logistic regression did not identify any characteristics to predict distant metastasis in staged patients (chi-squared p = 0.162). Two guidelines used postoperative results to inform radiological staging decision; 68/227 (30%) of staged patients met these guideline criteria, five of eight patients with distant metastasis did not meet current guideline criteria for radiological staging.

Over 50% of patients with distant metastasis did not meet current guideline criteria for radiological staging and would have remained undiagnosed if current guidelines were followed. This study had an acceptable detection rate of 3.5% for distant metastasis. We therefore recommend radiological staging in all patients with positive sentinel lymph node biopsy.