The prognostic relevance of the mitotic activity index in axillary lymph node-negative breast cancer.

The aim of the present study is to look at the mitotic activity index (MAI) as a prognostic factor in a prospective population-based cohort of lymph node-negative invasive breast cancer patients. Analyses were based on 2,048 breast-conserving therapies in 1,971 patients, node-negative, and without any form of adjuvant systemic therapy with long-term follow-up. The 15-year distant metastases-free survival (DMFS) for women ≤55 years was 88.3 % for low MAI values (≤12) versus 73.4 % for high MAI values (>12); (HR 2.8; 95 % CI 1.8-4.4; p < 0.001). Multivariate analyses for DMFS showed significance for MAI. For MAI and Bloom-Richardson grading, by performing a likelihood ratio test, we showed the statistical significance for both. For women >55-years, the MAI was not an independent significant factor. We also confirmed the above findings for disease-specific survival. When multi-gene assays are not available, the MAI remains a robust prognostic marker in women younger than 55 years of age with early node-negative breast cancer.