Axillary sentinel lymph node biopsy (SLNB) is a single lymph node or first set of nodes that receive direct lymphatic drainage from a primary tumor. The number of nodes examined, minimal surgeon experience may increase false negative rates (FNR), the results reported in the literature are however inconsistent. The adequate number of SLN required for achieving a low FNR remains controversial especially those receiving neoadjuvant chemotherapy (NAC).
We retrospectively evaluated 539 patients between Jan 1989 – Oct 2015, Median age 64 (30 – 91) with a median follow-up of 8.9 (0.03, 26.8) years. SLNB was performed post NAC in 210 clinically N0 breast cancers by community breast surgeons across three rural surgical practices. Logistical regression analysis was used to assess the relationship of recurrence with SLNB using SAS ver.9.3. FNR was calculated by evaluating 70/210 patients who received AD (Axillary dissection) post SLNB and were found to have positive nodes on AD. Technique used for SLNB was recorded.
Six patients had positive nodes on AD despite a negative SLNB yielding an overall FNR of 8.5% (6/70) post NAC. All FN patients had ≤ 2 SLNs removed, they were in Isosulfan blue dye (IBD) group and had a Ki67>10%. The number of SLNs identified ranged from 1 to 9 (mean, 2.2; median 2). FNR for 2 or more SLNs removed was 2.8% (2/70), above 3 SLNs FNR was 0%. Three patients had SLNB failure (no nodes detected). (IBD) was used in 83/198 (42%), technetium sulfur colloid (TSC) in 101/198 (51%) both 12/198 (6%). Among patient with SLNB, the local recurrence was 5.34%. No adjuvant radiation increased the likelihood of LR by 2.92-fold. LR rates were similar with IBD or TSC (p = 0.79).
FNR of 2.8% or lower can be achieved with surgeons in rural practices with limited volumes if ≥ 2 SLN are removed. LR rates were consistent with Z-0011. Surgeons in our study preferred mostly blue dye due to cost issues and does not affect LR. Excisional biopsies tend to be common in rural practices although not recorded in our study may also have a role to play since disruption may alter the lymphatic flow leading to FNR. We hypothesize that there might be an optimal threshold number of SLNs removed to achieve acceptable FNR 0-5% if 2-3 SLNs are removed. NAC had acceptable overall FNR of 8.5%.
Clinical trial identification
Legal entity responsible for the study
Kymera Independent Physicians
All authors have declared no conflicts of interest.