Limitation in gamma probe localization of the sentinel node in breast cancer patients with large excisional biopsy

Background: Radiolocalization and selective biopsy of the sentinel node to correctly predict the status of remaining lymph nodes may provide an alternative to axillary dissection in selected breast cancer patients with clinically negative lymph nodes. Study Design: In a nonrandomized, multicenter clinical trial, gamma probe localization for lymphatic mapping and sentinel node biopsy along with axillary dissection was performed on 75 patients with invasive breast cancer and clinically negative lymph nodes. The accuracy of the sentinel node biopsy to correctly predict the status of the remaining axillary lymph nodes was established through standard pathologic investigation. Results: A sentinel node was identified in 70 of 75 patients with a technical success rate of 93%. Of these 70 patients, 21 (30%) had axillary nodal metastases identified pathologically. Four of these 21 (19%) had sentinel nodes negative for metastases. All 4 false-negative patients had prior excisional biopsies. The false-negative group had a larger mean maximal biopsy dimension than the true-positive group. Eleven of the 21 patients with axillary metastases had a diagnosis made by core needle biopsy with no false negatives. Conclusions: The accuracy of the sentinel node biopsy in correctly predicting the status of remaining axillary lymph nodes may be limited in patients with large excision before radiolocalization of the sentinel node. Our findings suggest that excisional biopsy should be avoided prior to lymphatic mapping for sentinel node biopsy.