Background Lymphatic mapping with sentinel lymphadenectomy (SL) has become more widely used as an alternative to axillary dissection for the staging of breast cancer. This study was conducted to evaluate the potential associations of patient and tumor characteristics with the lymphatic mapping failure rate. Study design Between September 1996 and April 2003, 1,094 breast cancer patients participated in a single-institution prospective SL protocol, which was conducted using technetium 99 m sulfur colloid alone to identify sentinel lymph nodes. During the validation phase, consisting of the first 80 patients, all patients had SL followed by axillary dissection. Beginning with the 81st patient, the standard technique consisted of radiolabeled colloid injection in a peritumoral distribution 16 to 24 hours before the operation, followed by SL alone for node-negative patients. Results Of 1,094 consecutive patients, 62 (5.7%) did not map. Patients having more than 10 involved lymph nodes had a significantly higher incidence of mapping failure (40.9%) than those who were node-negative (5.3%) (odds ratio = 9.19, p = 0.002). Age was a factor predictive of mapping failure for node-negative patients 70+ years of age (odds ratio = 3.14, p = 0.018). Biopsy technique, tumor size, tumor location, cell type, and surgeon experience were not predictors of mapping failure, regardless of node status. Conclusions The lymphatic mapping failure rate was associated with both anatomic and pathologic factors. Patients with extensive nodal involvement had a significantly greater chance of mapping failure. Among node-negative patients, those who were older were more likely to have mapping failure than those who were younger, suggesting that decreased breast density in postmenopausal women might provide an anatomic explanation for nonmapping.
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