A pilot study to assess the utility of SPECT/CT-based lymph node imaging to localize lymph nodes that drain the arm in patients undergoing treatment for breast cancer

Image-guided treatment planning that minimizes irradiation of critical lymph nodes (LNs) may reduce the incidence and severity of long term complications following breast cancer treatment. This localization cannot be obtained with conventional imaging techniques and we undertook this proof of concept study to determine whether a coordinated use of SPECT and CT has sufficient precision to inform radiation planning and potentially lessen the incidental exposure of critical LNs. Thirty-two consecutive women with breast cancer were injected in the arm ipsi-lateral to their breast cancers prior to radiation treatment with 0.5 mCi of filtered ^99mTc-sulfur colloid and underwent scanning with a hybrid device which combined a dual-head SPECT camera and a low-dose, single slice CT scanner. The number of visualized LNs as well as their locations, maximum counts, and total uptake were recorded. Coordinates derived from the SPECT/CT fusion images were used to map LN locations onto the 3D radiation treatment planning system. A mean of 3.4 (SD 2.0) lymph nodes were detected in each subject. Level I and II LNs were detected more often in patients who had sentinel node biopsies, and more supraclavicular nodes were detected in patients who had undergone axillary dissection (P < 0.001). SPECT-CT derived LN coordinates were successfully mapped onto radiation simulation CT scans for all patients. SPECT/CT fusion images localize the LNs draining the arm after breast cancer surgery. These finding suggest that SPECT/CT may be helpful in minimizing incidental LN irradiation and in directing breast cancer therapy to reduce long-term morbidity.