Abstract P3-01-06: Sentinel lymph node biopsy after NACT: Results of a validation study in large/locally advanced breast cancer patients

Abstract

Abstract Background: Sentinel lymph node biopsy (SLNB) is the current standard of care for surgical staging of clinically node negative axilla (N0) early breast cancer patients undergoing primary surgery. SLN- identification rate (IR) of 90% and SLN- false negative rate (FNR) of 10% are considered minimum acceptable indices for SLNB. Its role in staging axillae in patients undergoing post-NACT surgery is somewhat unclear. In India, and most low-and-middle income countries, large operable breast cancers (LOBC) and locally advanced breast cancers (LABC) constitute a large proportion of breast cancer patients treated. These patients are usually are treated with NACT, followed by surgery and radiation therapy. In a prospective validation SLNB study, we investigated the accuracy of SLNB in staging post-NACT N0 axilla in a patient cohort that were LOBC or LABC at the time of initial presentation. Methods: Hundred consenting non-inflammatory LOBC/LABC patients (mean age 49.3+8.6; index stage T3,N0-1=21; T4b,N0-1=33; T1-3,N2a=24; T4b,N2a=22) who were N0 after NACT at time of surgery (Breast conservation surgery in 19, Mastectomy in 81) were included. Majority had Infiltrating ductal carcinoma (n=87), and grade II/III tumors (n=93); 45 were hormone receptor positive (+), 29 had HR negative (-) HER2(+); and 26 had triple negative breast cancer on IHC sub-typing. Commonest NACT regimen used was Anthracycline followed by taxanes in 83. SLNB was performed using low-cost methylene-blue and 99mTc-Antimony-colloid, which were produced in-house using well standardized protocols, with clearance of the institutional ethics committee. Irrespective of the SLN histology, a complete axillary dissection (ALND) was carried out in all. SLN-IR and SLN-FNR were calculated, comparing the histological status of the SLN and the ALND specimen. Factors predicting non-identified SLN and false negative SLN were evaluated in uni-variate and multi-variate analysis. Results: With a combination of methylene blue dye and radiopharmaceutical, the SLN-IR was 81%. Mean number of SLN removed was 2.4+/-1.02. Mean number of nodes removed at ALND was 13.3+/-2.2. SLN-IR varied significantly (p<0.05) per index stage, and were- 90.4% in T3,N0-1; 84.4% in T4b,N0-1; 83.3% in T1-3,N2a; and 63.6% in T4bN2a. The FNR was 17.3% for the whole cohort. FNR varied significantly (p<0.05) per index stage, and were- 8.3% in T3,N0-1; 14.9% in T4b,N0-1; 22.2% in T1-3,N2a; and 30% in T4bN2a. Factors found predictive of non-identified SLN were tumor stage T4b, nodal stage N2a, extra-nodal spread, and LVI. Factors found predictive of FNR SLN were tumor stage T4b, nodal stage N2a, and extra-nodal spread. Conclusions: Considering SLN-IR of 90% and SLN-FNR of 10% as acceptable standards, SLNB in post-NACT N0 patients undergoing surgery was not found robust in staging the axilla, with the exception of patients with index stage T3,N0-1 who had SLN-IR of 90.4% and SLN-FNR of 8.3%. Patients with (pre-NACT) skin involvement(T4b), matted axillary nodes(N2a) and LVI are fraught with high-risk of non-identification and false-negative SLNB. Citation Format: Agarwal G, Gambhir S, Lal P, Rajan S, Krishnani N, Mishra A, SabaRetnam M, Agarwal A, Chand G, Verma AK, Mishra SK, Kumari N, Agrawal V, Kheruka SC. Sentinel lymph node biopsy after NACT: Results of a validation study in large/locally advanced breast cancer patients. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P3-01-06.