cT2 patients scheduled for primary chemotherapy (with or without a clinically involved axilla - cN0/1) who have disease-free sentinel nodes (pN0) after primary chemotherapy, are directed to "SNB only": i.e. no further treatment to the axilla.

cT2 patients scheduled for primary chemotherapy (with or without a clinically involved axilla - cN0/1) who have metastatic sentinel nodes (pN1) on sentinel node biopsy (SNB) will undergo axillary dissection (AD) i.e. surgical removal of most axillary lymph nodes.

Colloidal radiotracer (99Tc) is injected into the breast near the cancer. The radiotracer moves in the lymph ducts to accumulate in the first lymph nodes (almost always in the axilla) to receive lymph from the breast area containing the cancer. Lymphoscintigraphy is used to check for the presence of radioactivity in the axilla. Some hours later, during breast surgery, a radioactivity-detecting probe is used to identify "hot" lymph nodes (sentinel nodes) and aid their surgical removal from the axilla. These nodes are examined histologically (intraoperatively) for the presence of cancer. If they are disease-free the axilla will be left intact (no further axillary treatment given); if they contain cancer most lymph nodes in the axilla will be removed surgically (axillary dissection).

DFS and OS are reckoned from date of surgery. DFS is time to recurrence or death, whichever occurred first. OS is time to death for any cause. Time is censored for living patients who are event-free at most recent follow up. OS and DFS curves are estimated using the Kaplan-Meier method and compared using the log-rank test. To compare DFS and OS in the SNB only and SNB + AD groups, propensity scores are estimated to account for bias due to non-random assignment to SNB vs SNB + AD

In patients given only sentinel node biopsy the proportion of patients who develop disease in the axilla will be calculated.

The response of the cancer to primary chemotherapy (complete response, partial response, stable disease, disease progression) will be related to overall outcomes.