Lymphatic drainage patterns on early versus delayed breast lymphoscintigraphy performed after injection of filtered Tc-99m sulfur colloid in breast cancer patients undergoing sentinel lymph node biopsy

The axillary lymph node status is the most important predictor of prognosis and aids in breast cancer treatment planning. Patients with breast cancer now frequently undergo sentinel lymph node (SLN) biopsy rather than axillary lymph node dissection to determine the status of the regional lymph nodes. However, the optimal timing of radionuclide injection relative to the timing of SLN biopsy remains controversial. The objective of this study was to compare the lymphatic drainage patterns on lymphoscintigraphy performed at 15 minutes to 4 hours and at 18 to 24 hours after injection of filtered Tc-99m sulfur colloid, and to determine whether, over time, radiocolloid migrates to second-echelon nodes that are not the SLNs. Fifteen women with breast cancer (mean age, 55 years; range, 38-78 years) were scheduled to undergo SLN biopsy after each received an injection of 18.5 MBq (0.5 mCi) filtered Tc-99m sulfur colloid into the breast parenchyma surrounding the tumor or biopsy cavity. Both early (15 minutes to 4 hours after radionuclide injection) and delayed (18-24 hours after radionuclide injection) lymphoscintigraphy was performed in each patient. SLN biopsy was performed, followed by completion axillary lymph node dissection and planned breast surgery. In each patient the patterns of distribution of the radionuclide in the lymph nodes were the same on early and delayed lymphoscintigrams. These findings, that the distributions of radionuclide in lymph nodes are identical on early and delayed images obtained after injection of filtered Tc-99m sulfur colloid, suggest that performing SLN biopsy on the day after injection does not diminish the accuracy of the technique in predicting the potential site of metastasis in the regional lymph nodes in patients undergoing this procedure for breast cancer.