Axillary node status in breast cancer patients prior to surgery by imaging with Tc-99m humanised anti-PEM monoclonal antibody, hHMFG1.

In early breast cancer axillary nodes are usually impalpable and over 50% of such patients may have an axillary clearance when no nodes are involved. This work identifies axillary node status by imaging with a Tc-99m radiolabelled anti-Polymorphic Epithelial Mucin, humanised monoclonal antibody (human milk fat globule 1), prior to surgery in 30 patients. Change detection analysis of image data with probability mapping is undertaken. A specificity of 93% and positive predictive value of 92% (both 100% if a second cancer in the axilla with negative nodes is considered) were found. A strategy for combining negative imaging with the sentinel node procedure is presented.

Efficacy of immunoscintigraphy for detection of lymph node metastases.

The size of a lymph node is not in principle a limitation for the detection of cancer by Nuclear Medicine techniques. A radioactive pinhead is detectable if it has enough radioactivity on it. The approach of Nuclear Medicine to the demonstration of impalpable lymph nodes or to those lymph nodes detected by radiological techniques that are under 1 cm as to whether or not they contain cancer, is to increase the activity attached to cancer cells in such a lymph node as much as possible and to use sophisticated image analysis techniques to distinguish such uptake from its environment. This may be undertaken using a non specific technique such as F-18 Deoxyglucose and Positron Emission Tomography which is highly sensitive and which has been successful. The alternative approach is to use a highly specific and sensitive agent, such as a radio-labelled peptide or a radio-labelled monoclonal antibody together with image analysis. This paper describes these approaches and in particular the use of Tc-99m SM3 monoclonal antibody in the detection of impalpable axillary nodes in patients with breast cancer before surgery, using a change detection analysis providing a probability map of the significance of uptake of this radiopharmaceutical. It is a robust approach, providing the patient and the surgeon with information as to the likely need for extensive axillary surgery well prior to operation. A negative study should be followed by a sentinel node evaluation at surgery.