Background: The role of occult metastases (micrometastasis or isolated tumor cells [ITC]) in sentinel lymph nodes (SLN) remains a field of debate and speculation. The purpose of this systematic review and meta-analysis was to investigate the prognostic relevance of occult metastases in SLN.

Methods: We searched PubMed, without year or language restriction through June 2011, for studies on patients with invasive breast cancer with micrometastasis or ITC in the SLN and presented Hazard Ratios (HR) on Overall Survival (OS) / Disease-Free Survival (DFS) or enough data for HR-calculation. We used fixed- or random-effects meta-analyses, as appropriate, to calculate pooled estimates of HR. Results: Fifteen studies were considered eligible. Of those, 3 studies were excluded due to the lack of data for HR-calculation. Both the presence of ITC (5 studies; 1264 patients with ITC) and micrometastasis (10 studies; 1093 patients with micrometastasis) were associated with worse DFS (pooled HR 1.29, 95% Confidence Interval [CI]: 1.09−1.52, P-value = 0.002 for ITC, pooled HR 1.45, 95% CI: 1.28−1.64, P-value < 0.001 for micrometastasis). No significant differences were observed regarding OS neither for the presence of ITC (5 studies; 877 patients with ITC; pooled HR 1.20, 95% CI 0.98−1.46) nor for micrometastasis (8 studies; 1094 patients with micrometastasis; pooled HR 1.36, 95% CI: 0.98−1.88).

Conclusion: Based on the current evidence, it seems that the presence of occult metastasis in SLN is of prognostic significance in regard to DFS. However, the clinical significance of this difference is questioned since it cannot be translated into differences in OS. In anticipation of randomized trials aimed to evaluating the optimal management of each category of tumor burden within SLN, current evidence suggest a limited clinical significance of occult metastases in SLN.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P3-07-34.