Abstract P5-06-02: Pathologic complete response (pCR) and prognosis following neoadjuvant chemotherapy plus anti-HER2 therapy of HER2-positive early breast cancer (EBC)
Authors: Loibl Sibylle , Untch Michael , Buyse Marc , Robidoux André , Gianni Luca , Schneeweiss Andreas , Conte Pierfranco , Piccart Martine , Bonnefoi Hervé , Jackisch Christian , Nekljudova Valentina , Costantino Joseph , Valagussa Pinuccia , Neate Colin , Gelber Richard , Poncet Coralie , Squifflet Pierre , Saad Everardo , Heinzmann Dominik , Denkert Carsten , Geyer Charles E , Cortes Javier , Guarneri Valentina , de Azambuja Evandro , Cameron David , Ismael Gustavo , von Minckwitz Gunter , Wolmark Norman , Cortazar Patricia 
Published: March 2020

Background: The achievement of pCR (breast and axilla) is strongly prognostic for event-free (EFS) and overall survival (OS) in EBC (Cortazar 2014), and modulation of therapy improves long-term outcomes for patients with HER2-positive disease not achieving pCR (Von Minckwitz 2019). We sought to investigate prognostic factors for EFS and OS among patients with and without pCR following neoadjuvant systemic treatment consisting of chemotherapy plus anti-HER2 therapy.

Methods: We used individual data from 3,710 patients randomized in 11 neoadjuvant trials for HER2-positive EBC with N≥100 patients enrolled, available data for pCR, EFS, and OS, and follow-up ≥3 years. We assessed baseline clinical tumor size (cT) and clinical nodal status (cN) as prognostic factors using stratified (by trial and treatment) Cox models separately for hormone-receptor (HR)-positive vs. HR-negative disease, and for patients who achieved pCR (pCR+; ypT0/is, ypN0) vs. patients who did not achieve pCR (pCR-).

Results: The median follow-up overall was 61.2 months. The table shows hazard ratios and 5-year Kaplan-Meier estimates of OS (5yr OS) according to HR and pCR. Comparable results were observed for EFS. Both cT (1-2 vs. 3-4) and cN (cN- vs. cN+) were independent prognostic factors for OS in most subsets, including in pCR+ patients.

Conclusions: These results confirm that patients achieving pCR have far better long-term outcomes than patients who do not, and that traditional poor prognostic features namely tumour size and nodal status remain important even after a pCR, with no clear evidence that the relative impact of unfavourable (cT3-4 or cN+) features is different in patients who achieve a pCR than in those who did not.

Key words: neo-adjuvant therapy, HER2-targeted therapy, pathological complete response, prognostic factors, overall survival

Funding: German Breast Group

HR pCRBaseline cT/cN DeathsPatients5yr OS (%)Hazard ratio* [95% CI]HR+ pCR+cT1-2/cN-521298.6%1.0 (reference)(N= 637)cT3-4/cN-46592.9%0.49 [0.21-1.14]cT1-2/cN+720095.1%0.82 [0.34-1.99]cT3-4/cN+1016094.0%0.40 [0.13-1.25]HR+ pCR-cT1-2/cN-1737796.3%1.0 (reference)(N=1399)cT3-4/cN-2514381.8%0.51 [0.36-0.73]cT1-2/cN+4844888.9%0.71 [0.49-1.03]cT3-4/cN+6443184.9%0.36 [0.23-0.58]HR- pCR+cT1-2/cN-319698.1%1.0 (reference)(N=860)cT3-4/cN-89090.4%0.56 [0.32-0.98]cT1-2/cN+1928092.4%0.49 [0.24-0.98]cT3-4/cN+3029489.5%0.27 [0.12-0.64]HR- pCR-cT1-2/cN-2114083.2%1.0 (reference)(N=814)cT3-4/cN-207871.4%0.46 [0.34-0.64]cT1-2/cN+4225181.6%0.76 [0.53-1.09]cT3-4/cN+11634561.9%0.35 [0.22-0.56]*Hazard ratio cT1-2/cN- vs. higher risk cohorts

Citation Format: Sibylle Loibl, Michael Untch, Marc Buyse, André Robidoux, Luca Gianni, Andreas Schneeweiss, Pierfranco Conte, Martine Piccart, Hervé Bonnefoi, Christian Jackisch, Valentina Nekljudova, Joseph Costantino, Pinuccia Valagussa, Colin Neate, Richard Gelber, Coralie Poncet, Pierre Squifflet, Everardo Saad, Dominik Heinzmann, Carsten Denkert, Charles E Geyer, Javier Cortes, Valentina Guarneri, Evandro de Azambuja, David Cameron, Gustavo Ismael, Gunter von Minckwitz, Norman Wolmark, Patricia Cortazar. Pathologic complete response (pCR) and prognosis following neoadjuvant chemotherapy plus anti-HER2 therapy of HER2-positive early breast cancer (EBC) [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P5-06-02.