Factors affecting the negative predictive value of positron emission tomography/computed tomography for axillary lymph node staging in breast cancer patients.

Background/objective: Axillary lymph node staging (ALNS) is an important step in the treatment of breast cancer and sentinel lymph node biopsy (SLNB) is a standard procedure for ALNS. Recently, the use of positron emission tomography/computed tomography (PET/CT) for whole body staging in patients with breast cancer has been increasing. The negative predictive value (NPV) of the specific diagnostic modality is the crucial value for excluding axillary lymph node metastasis (ALNM) and guiding the decision not to proceed with axillary lymph node dissection. The aim of this study was to identify patient groups in which PET/CT yields a high NPV for ALNS.

Methods: We reviewed data from the records of 262 patients with breast cancer who underwent PET/CT before surgery between February 2009 and March 2018. We searched for factors associated with pathological axillary lymph node metastasis in patients with negative ALNM on PET/CT. Then, we calculated the NPV of PET/CT for ALNS in the patient group without the identified factors and in all patients.

Results: Age ≥75 years and tumor size on ultrasonography (US) ≥ 15 mm were the associated factors; the NPV of PET/CT in patients without these factors compared to all patients was 97.2% versus 88.7%.

Conclusion: The NPV of PET/CT for ALNS in patients younger than 75 years and with tumor size on US < 15 mm is higher than that in all patients and comparable to the NPV of SLNB reported in previous studies (90.1-97.0%).