Credentialing for breast lymphatic mapping: How many cases are enough?

Objective To evaluate credentialing issues for sentinel lymphatic mapping f or breast cancer. Summary Background Data The sentinel lymph node (SLN) is defined as the fir st lymph node receiving lymphatic drainage from a tumor. The SLN accurately reflects the status of the axillary nodes in patients with early-stage bre ast cancer, and SLN mapping is gaining widespread acceptance. Few of the ma ny published feasibility studies of lymphatic mapping for breast cancer hav e adequate numbers to assess credentialing issues for this new procedure. Methods Five hundred consecutive SLN biopsies were performed at one institu tion, over a 20-month period, by eight surgeons, using isosulfan blue dye a nd technetium-labeled sulfur colloid. The authors reviewed each surgeon's s uccess rate in finding the SLN, and false-negative rate, relative to level of experience with the technique. Results Lymphatic mapping performed by an experienced surgeon (surgeon A, B , or C) was associated with a higher success rate (94%) than when it was pe rformed by one with less experience 86%. Ten failed mapping procedures occu rred in the first 100 cases. For each of the ensuing 100 cases, there were eight, six, six, and four failed mapping procedures, suggesting that increa sing experience does not eradicate failed mapping procedures completely. Th e false-negative rate among 104 patients in whom axillary dissection was pl anned in advance was 10.6% (5/47). Most false-negative results occurred ear ly in the surgeon's experience: when the first six cases of every surgeon w ere excluded, the false-negative rate fell to 5.2%(2/38). Conclusions with increasing experience, failed SLN localizations and false- negative SLN biopsies occur less often. Combined dye and isotope localizati on, enhanced histopathology, a backup axillary dissection, and judicious ca se selection are required to avoid the high false-negative rate of one's ea rly experience.