Abstract P2-01-03: Sentinel node procedure before or after neoadjuvant chemotherapy in clinically node negative or positive patients; results from 3 phase III studies of the Dutch breast cancer trialists' group (BOOG)
Authors: Tjan-Heijnen Vivianne C , Vriens Birgitte E , Aarts Maureen J , Kroep Judith R , van de Velde Cock J , Liefers Gerrit-Jan , Charehbili Ayoub , Peer Petronella G , de Boer Maaike 
Published: May 2015

Abstract
Background
In breast cancer patients treated with neoadjuvant systemic therapy, the timing of the sentinel node (SN) procedure in patients with clinically node-negative disease (cN0) at diagnosis and the role of the SN procedure after neoadjuvant therapy in patients with initially clinical node-positive disease (cN+) still remains to be elucidated.
Methods
Between February 2006 and May 2012, 657 patients were enrolled in three clinical trials on neoadjuvant systemic therapy under the auspices of the Dutch Breast Cancer Research Group (BOOG). In the INTENS and NEO-ZOTAC study, patients were treated with TAC or AC-T neo-adjuvant chemotherapy (doxorubicin (A), cyclophosphamide (C) and docetaxel (T)). In the TEAM IIa trial, patients were treated with neoadjuvant endocrine therapy (exemestane for 6 months). Timing of the SN procedure in cN0 disease mainly depends on local policy and period of inclusion. We compared the pN0 rate after SN procedure performed before versus after neoadjuvant systemic therapy, in patients with cN0 disease at initial diagnosis. Further, we assessed the SN negative and the false-negative sentinel node rate in patients with initially cN+ breast cancer and conversion to cN0 when treated with neoadjuvant systemic therapy. The false-negative rate was obtained by dividing the number of patients who were SN-negative but non-SN positive by the number of patients who had a positive SN or a positive non-SN.
Results
In total, 271 patients (n=93 INTENS, n=107 NEOZOTAC, n= 71 TEAM IIa) underwent a SN procedure (n=233 cN0; n=38 cN+). Of patients with cN0 breast cancer at diagnosis, 131 (56%) underwent the SN procedure before and 102 (44%) after neoadjuvant systemic therapy, with ypN0(sn) or ypN0(i+)(sn) in 90/131 (69%) and 69/102 (68%) patients, respectively. Patients with initially cN+ disease who converted to cN0 disease after systemic therapy had a negative SN in 29% (11/38) of cases. The false-negative rate was 20% (6 of 30). More detailed analyses will be presented at the meeting.
Conclusion
To our knowledge, this is the first study comparing the impact of the timing of the sentinel procedure in patients with cN0 disease. We showed, that irrespective of the timing of the SN procedure - before or after neoadjuvant systemic therapy - in patients with cN0 breast cancer at diagnosis, two-third of patients had a negative sentinel node. In patients who converted after neoadjuvant chemotherapy from cN+ to cN0 the false negative sentinel node rate was 20%.
Citation Format: Vivianne C Tjan-Heijnen, Birgitte E Vriens, Maureen J Aarts, Judith R Kroep, Cock J van de Velde, Gerrit-Jan Liefers, Ayoub Charehbili, Petronella G Peer, Maaike de Boer. Sentinel node procedure before or after neoadjuvant chemotherapy in clinically node negative or positive patients; results from 3 phase III studies of the Dutch breast cancer trialists' group (BOOG) [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P2-01-03.