International consensus on axillary staging after neoadjuvant chemotherapy in node-positive breast cancer.

INTRODUCTION

There is a lack of consensus on the eligibility thresholds and technical standards of minimally invasive axillary staging techniques including targeted axillary dissection (TAD), marked lymph node biopsy (MLNB) and sentinel lymph node biopsy (SLNB) in node-positive breast cancer responding to neoadjuvant chemotherapy (NAC).

METHODS

Consultant breast surgical oncologists from OECD countries were invited to participate. Statements developed from the literature, guidelines, and steering-committee were distributed to the panellists and consensus was investigated (≥70% agreement). Latent class analysis investigated the association between surgeon characteristics and axillary de-escalation.

RESULTS

Of 574 surgeons (97.7% with access to axillary marking/localisation), 471 (82.1%) completed Round 2. The preferred axillary approach in cN1 (82.5% agreement) and cN2a (77.4%) patients converting to ycN0 was TAD, in preference to MLNB or SLNB. Eligibility for TAD was agreed for three or fewer involved nodes pre-NAC (84.1%) but was not agreed for four or more nodes (40.1%). Consensus supported marking only a single pathological node (≥78%), before NAC (93.8%), with localisation (87.3%) and intra-operative confirmation (93.6%). TAD should include resection of all SLNs (91.9%), all abnormal palpable nodes (91.9%) and at least one SLN is required (86.2%). Single-tracer with TAD (66.7%) and the retrieval of the marked node without SLNs (62.0%) did not reach consensus as sufficient staging. ALND was not required for isolated tumour cells in the TAD specimen (76.0%). There was significant geographic variation in axillary de-escalation. Surgeons with ≥20years experience (OR, 0.29, p = 0.005) and those working in centres with ≥300 breast cancers annually (OR, 0.30, p = 0.017) were more likely to de-escalate surgery.

CONCLUSION

International consensus supports TAD as the preferred technique for cN1 patients responding to NAC, with agreement on essential procedural steps. Precise eligibility criteria for TAD and the omission of ALND require further investigation.