Predictors of non-sentinel lymph node metastasis in breast cancer patients with positive sentinel lymph node (Pilot study).

BACKGROUND

Sentinel Lymph Node Biopsy (SLNB) procedure was found to be an accurate method of staging the axilla in patients with early stage breast cancer. The standard of care for breast cancer patients with positive SLN metastasis includes complete Axillary Lymph Node Dissection (ALND). However, in 40-70% of patients, the SLN is the only involved axillary node. Factors predicting non SLN metastasis should be identified in order to define subgroups of patients with positive SLN in whom the axilla may be staged by SLNB alone.

OBJECTIVES

To identify the factors predicting metastatic involvement of the non-SLNs in breast cancer patients having SLN metastasis.

PATIENTS AND METHODS

Data were collected and analyzed from 80 patients with early stage invasive breast cancer (T1, T2, N0, M0) who underwent SLNB at the Surgical Oncology Department, Kuwait Cancer Control Center (KCCC) between November 2004 and February 2009. SLNB was performed using a combined technique (radioactive colloid, and blue dye) in the majority of cases. In some cases, only one technique was used. Complete ALND was performed in the case of failure of SLN identification and in patients with positive SLN. Multiple variables (patient, tumor, and SLN characteristics) were tested as possible predictors of nonsentinel lymph node metastasis.

RESULTS

The mean age of patients at diagnosis was 46.6years. The median tumor size was 2cm. The SLN identification rate was 96.2% (77 out of 80 patients). The SLN was positive in 24 patients (31%), and half of these showed evidence of capsular invasion. The median number of SLNs removed was two. The median number of positive SLNs was one. The incidence of non-SLN metastasis associated with positive SLN was 50% (12 out of 24 patients). Lymphovascular invasion was found to be the only factor associated with non-SLN metastases. In addition, two trends were observed, though they did not reach the statistical significance: the first is that the majority of patients having capsular invasion of the SLN (8 out of 12 patients, 67%) had positive non-SLN metastasis, and the second is that the patients having more than one SLN metastasis were more likely to have non-SLN metastasis (4 out of 5, 80%).

CONCLUSION

In the current pilot study, only the lymphovascular invasion in the area of the primary tumor was found to be significantly related to the nonsentinel lymph node metastasis. There was a tendency toward higher incidence of nonsentinel lymph node metastasis associated with the number of positive SLN and capsular invasion of SLN, though this did not reach the statistical significance. This could be attributed to the small number of patients recruited. Further evaluation of the predictors of nonsentinel lymph node metastasis on a larger number of patients is required. The validation of these predictors in prospective studies may enable approximately half of early stage breast cancer patients with positive SLN to be staged with SLNB alone while avoiding the morbidity of unnecessary ALND.