Introduction of sentinel node biopsy and stage migration of breast cancer

The purpose of this study was to examine in a large population based group of breast cancer patients treated in a regular care setting whether the introduction of the Sentinel Node Biopsy (SNB) led to detection of a higher percentage of patients with positive regional lymph nodes.

The study includes 3665 early breast cancer patients, aged 30-85 years, diagnosed in the period 1997-2002 and registered at the Regional Cancer Registry of the Comprehensive Cancer Centre Middle Netherlands. During this period the SNB was introduced. The outcome of staging was compared for groups staged with or without SNB. A logistic regression model was used to adjust for age, calendar period and tumour size.

Overall a quarter of all patients over the period 1997-2002 underwent a SNB as method of lymphatic staging. The use of SNB clearly increased over time: from 2% in 1998 to 65% in 2002. The percentage node positive patients also rose significantly; before introduction of the SNB 30% of all patients were diagnosed with positive lymph nodes, and after SNB introduction this percentage was 40%. The increase is largely explained by the increase of patients diagnosed with only micrometastases. Adjustment did not change the results.

In conclusion, introduction of the SNB in early breast cancer led to significant upstaging of breast cancer patients treated in a regular care setting, due to the detection of more micrometastases. Since the relevance of micrometastases for long term survival is not yet known, this upstaging potentially led to over treatment of patients. On the other side, for some patients axillary lymph node dissection was prevented by the SNB procedure, preventing comorbidity.