Sentinel node micrometastases in breast cancer do not affect prognosis: a population-based study

Sentinel node biopsy (SNB) for axillary staging in breast cancer allows the application of more extensive pathologic examination techniques. Micrometastases are being detected more often, however, coinciding with stage migration. Besides assessing the prognostic relevance of micrometastases and the need for administering adjuvant systemic and regional therapies, there still seems to be room for improvement. In a population-based analysis, we compared survival of patients with sentinel node micrometastases with those with node-negative and node-positive disease in the era after introduction of SNB. Data from the population-based Eindhoven Cancer Registry were used on all (n = 6803) women who underwent SNB for invasive breast cancer in the Southeast Region of The Netherlands in the period 1996-2006. In 451 patients (6.6%) a sentinel node micrometastasis (pN1mi) was detected and in 126 patients (1.9%) isolated tumor cells (pN0(i+)). Micrometastases or isolated tumor cells in the SNB did not convey any significant survival difference compared with node-negative disease. After adjustment for age, pT, and grade, still no survival difference emerged pN1mi: [HR 0.9 (95% CI, 0.6-1.3)] and pN0(i+): [HR 0.4 (95% CI, 0.14-1.3)] and neither was the case after additional adjustment for adjuvant systemic therapy. Our practice-based study showed that the presence of sentinel node micrometastases in breast cancer patients has hardly any impact on breast cancer overall survival during the first years after diagnosis.