Sentinel lymph node biopsy (SLNB) prior to primary chemotherapy (PC) in breast cancer patients

Background: Lymph node status is the single most important determinant of prognosis and is used for planning adjuvant therapy. Patient selection and timing of SLNB for PC continue to evolve; SLNB prior to PC may allow more accurate initial staging and prognostication and guide decisions about adjuvant treatment. Methods: 78 patients (pts) who were treated in the Cambridge Breast Unit as part of Neo-tAnGo (a multicentre PC trial). 57 were identified as potentially suitable for SLNB pre-PC (clinically node negative, non-inflammatory tumours 2–5cm in size). 38 had axillary ultrasound, and of these, 18 had sonographically suspicious nodes. 12/18 had confirmed nodal metastasis on core biopsy (CB) and had direct ALND post-PC. The remaining 20 patients had innocent nodes or were CB negative, of whom 19 underwent SLNB. A total of 19 patients in this subgroup did not undergo axillary ultrasound; 16 of these proceeded to ALND post-PC and 3 to SLN biopsy pre-PC according to unit policy at the time. A total of 22 (19 + 3) pts were available for analysis of SLN biopsy pre-PC in terms of time to treatment compared to the remainder of the centre's cohort in the Neo-tAnGo study. 42, (22 SLNB + 20 node positive on CB), were analysed as having axillary pathological staging before PC and compared to the other patient cohort on study. Results: The SLN was successfully identified in all 22 pts using dual localisation techniques with a mean SLN harvest of 2.8 nodes per patient (range 1–10). 6/22 pts (27%) were node positive, and 5 had single SLN involvement (4 macro-; 1 micro-) and one had a macro- and a micrometastasis in 2 different nodes. The mean time from diagnosis to start of PC in the SLN group was 23 days (range 8–43) compared 18 days (range 7–36) for the comparator cohort on study (p=0.02). When all 42 pts with pathological axillary assessment were analysed (including clinically node positive pts with tumours >5cm), there was no significant difference in time from diagnosis to start of PC for pts undergoing CB and/or SLNB (21 days) compared with no axillary assessment (17 days) (wilcoxon test p=0.10). The mean number of nodes removed on completion ALND was 9 (range 4–16). There was no evidence of any viable tumour or fibrosis in any of the non-SLN's (NSLN) examined. Amongst the group of 18 ultrasound/CB positive pts who underwent ALND without SLNB, nodal disease was found in 9 (50%) with evidence of pathological downstaging in 4 (22%). Conclusion: There is potential loss of staging information when SLNB is performed after PC and the clinical significance of a negative SLNB result in this setting is uncertain. A combination of axillary ultrasound (with CB) and SLNB can more accurately stage the axilla without significant overall delays in commencement of PC for clinically node positive and negative pts. Downstaging of disease in NLSN may occur in response to PC with a lower NSLN rate (0%) when compared to primary surgical treatment in smaller tumours (15–25%)