Stage migration after introduction of sentinel lymph node dissection in breast cancer treatment in Denmark: a nationwide study

Purpose: To estimate the size and therapeutic consequences of stage migration after introduction of sentinel lymph node dissection (SLND) in breast cancer treatment in Denmark.

Patients and methods: We compared the distribution of lymph node metastases in breast cancer patients operated in 1993-1996 and 2005-2008; before and after introducing SLND. The study was based on data from the national Danish Breast Cancer Cooperative Group (DBCG) database.

Results: We included 24,051 patients in the study; 10,231 patients from the first period and 13,820 from the second period. The proportion of patients having macrometastases was not significantly different in the two periods, whereas the proportion of patients with micrometastases increased from 5.1% to 9.0% (P<0.0001). However, this only resulted in an estimated change, from 7.8% to 8.8%, in the proportion of patients offered adjuvant systemic treatment due to positive nodal status as the only high-risk criterion, when using today's criteria for risk-allocation. In addition, we found that negative hormone receptor status was associated to negative nodal status when adjusted for confounders (odds ratios (OR) 0.83, P<0.0001).

Conclusion: Introduction of SLND in breast cancer treatment in Denmark has resulted in a stage migration on 4% due to identification of more micrometastases. However, this stage migration has only minor impact on patients offered adjuvant systemic treatment because nodal status today is less important in risk-allocation.