The overall goal of this study is to determine how FDG-PET can be incorporated into the assessment of the axilla in the staging and treatment of women with early stage breast cancer.

A multicentre, prospective, diagnostic accuracy study will be conducted evaluating the ability of positronic emission tomography using fluorodeoxyglucose (FDG-PET) to detect the presence or absence of axillary lymph node metastases in newly diagnosed breast cancer patients with no clinical evidence of spread of disease beyond the breast.

Patients will have histologic confirmation of invasive breast cancer and will have a FDG-PET scan prior to axillary node assessment. All patients will have a sentinel node biopsy if any sentinel nodes can be located. Patients with a positive sentinel node will have an axillary node dissection. The results of the PET will be compared to the reference standard of histologic examination of all excised (sentinel and non-sentinel) axillary lymph nodes which will be referred to as axillary node assessment. Sensitivity, specificity, positive and negative predictive values for PET-FDG will be determined.

Inclusion Criteria:

• Histologic diagnosis of invasive breast cancer,
• Resectable primary cancer.

Exclusion Criteria:

• The diagnosis of invasive breast cancer was made more than 3 months prior to registration,
• Patient and/or surgeon are not willing to proceed with a SNB or AND after the PET scan is completed,
• Patient and/or surgeon are not willing to proceed with a level I and II AND if the SNB is positive, if the PET scan shows increased uptake in the ipsilateral axilla, or if the surgeon is still gaining experience in the performance of SNB,
• SNB or AND has already been done,
• Chemotherapy has been given or will be given prior to PET scan or SNB or AND,
• Significant serious concurrent medical problems (e.g., uncontrolled diabetes),
• Patient is pregnant or lactating,
• Patient is unable to lie supine and with both arms above their heads for PET scan,
• Known hypersensitivity to FDG,
• Clinical evidence of regional nodal metastases (fixed, matted axillary nodes),
• Clinical evidence of distant metastases.