Abstract P3-12-20: Outcomes of patients with pathologic complete response following neoadjuvant HER2-targeted therapy in patients with HER2+ early stage breast cancer
Authors: O'Shaughnessy Joyce , Oestreicher Nina , Fulcher Nicole , Tseng Wan-Yu , Beeks April , Moore Julia , Lalla Deepa 
Published: March 2022

BACKGROUND: Contemporary clinical trials of HER2-targeted therapies have shown benefits regarding recurrence and survival in patients (pts) with HER2+ early stage breast cancer. The outcomes of pts treated in community practice settings who had a pathologic complete response (pCR) to neoadjuvant therapy or who had residual disease at definitive surgery (non-pCR) have not been well characterized. This preliminary study aimed to describe the patient characteristics, disease-free survival (DFS) and overall survival (OS) in patients with and without pCR following neaoadjuvant HER2-targeted therapy in The US Oncology Network. METHODS: This retrospective cohort study identified pts diagnosed with stage I-III HER2+ breast cancer who initiated neoadjuvant HER2-targeted therapy in the community setting between April 1, 2014 - March 31, 2019. Pts were followed through the date of last visit, death, or study end (March 31, 2021), whichever occurred first. Data were collected from the US Oncology Network’s electronic medical record database, iKnowMed. Natural language processing/artificial intelligence was used to identify pts with pCR status and pts with disease recurrence during the study period. Patient profiles, risk of recurrence (RR), and time to recurrence (TTR) were assessed descriptively. Kaplan-Meier methods were used to evaluate DFS and OS from the start of neoadjuvant therapy. Results were stratified by pCR status. RESULTS: The study included 641 pts (median age, 55 years), 71% had non-pCR and 29% had pCR. The majority of pts were Caucasian (79%) or black (8%). At diagnosis, 78% of pts had stage I/II disease, and 21% stage III. Nearly 74% were HR+. With a median follow-up of 33 months, pts who had non-pCR had a higher risk of disease recurrence (10.3% vs 8.1%) and a shorter median TTR (18.6 vs 21.1 months) compared to pts with pCR. Three-year DFS (87.5% vs 92.2%) and OS (96.0% vs 98.8%) were lower in pts with non-pCR than with pCR. CONCLUSIONS:Findings from this real-world study of HER2+ early stage breast cancer pts who received neoadjuvant HER2-targeted therapy in the community setting suggested that pts with non-pCR had shorter DFS and OS outcomes than pts with pCR. Pts with non-pCR had a risk of recurrence of nearly 10% over approximately a 3-year time period . This residual risk of recurrence among non-pCR pts suggested a potential opportunity to improve long-term outcomes in this group. Future analyses, including HR subgroups, are planned as data mature and longer follow-up time is available. Results on additional pts with known pCR/non-pCR data, with longer follow-up, and outcomes by HR+ vs HR- status will be presented.

Disclosure DeclarationThis study was funded by Puma Biotechnology, Inc.

Outcomes of pts with pCR or non-pCR following neoadjuvant HER2-targeted therapyNon-pCRpCROverall CohortN=429N=185N=641Follow-up time, months, median (range)30.8 (0.0,81.6)38.4 (2.8,83.3)33.0 (0.0,83.3)Patients with recurrence, n (%)44 (10.3%)15 (8.1%)59 (9.6%)Time to recurrence, median (range)18.6 (0.0,42.4)21.1 (0.0,60.3)18.8 (0.0,60.3)Disease-free survival at 36 months87.5% (83.4,90.7)%92.2% (86.8,95.4)%89.0% (85.9,91.5)%Overall survival at 36 months96.0% (92.8,97.8)%98.8% (95.2,99.7)%97.0% (94.9,98.3)%

Citation Format: Joyce O'Shaughnessy, Nina Oestreicher, Nicole Fulcher, Wan-Yu Tseng, April Beeks, Julia Moore, Deepa Lalla. Outcomes of patients with pathologic complete response following neoadjuvant HER2-targeted therapy in patients with HER2+ early stage breast cancer [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P3-12-20.