Abstract PD8-03: Conversion rates from positive to negative axillary involvement in breast cancer patients presenting with biopsy-proven axillary metastases prior to primary systemic therapy (PST) – A transSENTINA subproject

Abstract

Abstract Background: Modern chemotherapy carries a high potential of converting patients with clinically suspicious axillary nodes (cN+) prior to PST to clinically (ycN0) or pathologically (ypN0) negative nodes after PST. Clinical and sonographical axillary assessment, however, may be inadequate and therefore pathological assessment of suspicious axillary nodes is recommended. We analyzed the association between clinical / pathological parameters and positive to negative conversion in patients with biopsy-proven axillary metastases in Arm C of the SENTINA trial (i.e. patients with “true conversion”). Methods: Arm C of the SENTINA trial included patients converting from cN+ to ycN0 through PST from a prospective study. We limited our analysis to patients who had biopsy-proven axillary involvement. Univariate regression analysis was carried out to assess the association between patients with vs. without axillary disease after PST in i) patients with biopsy-proven involvement and ii) patients without biopsy proof of metastases. Results: Among 596 patients in arm C of the SENTINA trial with clinically and or sonographically suspicious ipsilateral axillary nodes, 439 (73,7%) 157 (26,3%) patients had a biopsy. In 152 patients (96,8%), lymph node metastases were confirmed and in 5 patients (3,2%), no malignant cells were identified. In both groups, we found a significant association (p<0,05) between increased rate of axillary conversion and small tumor diameter after PST, absence of multifocality, absence of lymphovascular invasion (LVI), ER and/or PR negativity, HER2 negativity, triple negative disease, and complete pathological response (pCR). No multiple testing corrections were performed due to an exploratory setting. However, only among patients with biopsy-proven involvement prior to PST, we found grade-3-tumors to be significantly associated with reduced probability of residual axillary involvement (76.1 vs. 33.8%, compared to G1 and G2, p=0.0323). Conclusion: Our analysis demonstrates that in patients with biopsy-proven axillary involvement before NST, parameters associated with axillary conversion are similar to those among patients classified as having nodal disease based on clinical and or sonographical assessment (cN+). Our analyses demonstrate that in biopsy-proven axillary metastases before NST, modern chemotherapy regimens result in significant rates of axillary conversion. This underscores the need to deescalate axillary staging / treatment with the goal to further avoid unnecessary axillary surgery. Citation Format: Liedtke C, Kolberg H-C, Krajewska M, Bauerfeind I, Fehm T, Fleige B, Helms G, Lebeau A, Staebler A, Loibl S, Untch M, Kühn T. Conversion rates from positive to negative axillary involvement in breast cancer patients presenting with biopsy-proven axillary metastases prior to primary systemic therapy (PST) – A transSENTINA subproject [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr PD8-03.