Clinical implication of metastasis in the second most radioactive sentinel lymph node with nonmetastatic most radioactive node in patients with breast cancer

Background: Sentinel lymph node biopsy (SNB) using radioisotopes is a standard method for assessing axillary lymph node status in patients with breast cancer. Although preoperative lymphoscintigraphy can estimate the number of sentinel lymph nodes (SNs), multiple radioactive SNs are often identified, even when lymphoscintigraphy reveals only one SN. Importantly, metastases are not always observed in the most radioactive SN (hottest SN). This study aimed to determine the significance of metastases in the second or less radioactive SNs when the hottest SN is negative.

Methods: We retrospectively analyzed 114 patients with breast cancer with positive SNs who underwent axillary lymph node dissection. The clinicopathological characteristics, SN radioactivity, and axillary lymph node status were evaluated.

Results: Twenty-six patients exhibited metastasis in the second or less radioactive SNs without metastasis in the hottest SN. These patients had a lower risk of non-SN metastasis compared with those with metastasis to the hottest SN (P=0.03). Multivariate analysis identified metastasis in the hottest SN [hazard ratio (HR) 4.93, P=0.01] and the detection of ≥2 SNs by lymphoscintigraphy (HR 3.36, P=0.01) as independent predictors of non-SN metastasis. None of the patients with only one lymph node detected by lymphoscintigraphy and metastasis to the second or less SNs without metastasis to the hottest SN showed non-SN metastasis.

Conclusions: Patients with metastasis in the second or less radioactive SNs, but not in the hottest SN, have a lower risk of non-SN metastasis than those with a positive hottest SN. Combining radioactivity with lymphoscintigraphic information can enhance the accuracy of non-SN status prediction.