Modelling of the impact of replacing four-node sampling with sentinel lymph node biopsy within the NHS Breast Screening Programme

The aim of this study was to use the Association of Breast Surgery at the British Association of Surgical Oncology audit data to model the possible consequences of the rollout of sentinel lymph node biopsy (SLNB) across the NHS Breast Screening Programme. The lymph node status, invasive size, grade and number of operations were examined for 26,431 screen-detected invasive cancers diagnosed in women who were invited for screening between 1 April 2001 and 31 March 2004.

Seventy-five per cent of screen-detected invasive breast cancer had a negative nodal status. The average number of nodes removed in these cases was 10. If these cases had had their axilla assessed using SLNB, then the majority of women diagnosed with screen-detected breast cancer would have had a minimally invasive axillary procedure. Assuming that the protocol utilised during the ALMANAC study was continued, the 25% of cases with positive lymph nodes would require a second operation to clear the axilla. This would represent a 20% increase in the number of cases requiring a second therapeutic operation. In addition, as over 80% of these cases had less than five positive nodes found, a full axillary clearance may be overtreatment.

Analysis of the variation of lymph node positivity with size and grade demonstrates that these factors could be used to determine which women with a positive sentinel lymph node require a full axillary clearance and which women could be appropriately managed with a level 1 clearance, thus reducing the possible complications of lympho-edema.