Abstract P2-13-14: Pattern of recurrence after pathologic complete response after neoadjuvant chemotherapy in patients with early HER2-positive breast cancer: Real-world evidence
Authors: Kim Jee Hung , Lee Jii Bum , Bae Soong Joon , Ahn Sung Gwe , Jeong Joon , Kim Min Hwan , Kim Seul-Gi , Kim Gun Min , Kim Jee Ye , Park Hyung Seok , Park Seho , Park Byeong Woo , Kim Seung Il , Sohn Joohyuk 
Published: March 2022

Background The real-world risk of disease recurrence in patients with HER2-positive early breast cancer who achieved pathologic complete response (pCR) after neoadjuvant chemotherapy (NAC) and/or HER2-targeted therapy is unclear. This study aims to identify the patterns and risk factors of disease recurrence after NAC in patients with HER2-positive early breast cancer who achieved a pCR or not. Methods 930 HER2 positive early breast cancer patients who received NAC were identified in the Severance Breast Cancer Registry at the Yonsei Cancer Center and Gangnam Severance Hospital in Seoul, Republic of Korea, between 2006 and 2020. NAC included 3 regimens: only chemotherapy. (CTx), chemotherapy plus trastuzumab (CTx+H), and chemotherapy plus dual anti-HER2 therapy (TCHP). The pCR was defined as the absence of residual invasive cancer in the resected breast specimen and the axillary lymph nodes (ypT0/TisN0) after neoadjuvant systemic therapy. Recurrence of disease was defined as recurrence of ipsilateral locoregional invasive breast cancer, distant disease recurrence, or death. Results The median follow-up duration was 42.0 months (range 4-171), and median age was 51 years old (range 22-80). The rate of pCR was 52.2% (485/930). Depending on the achieved a pCR, the loco-regional recurrence rate was 4.0% (18/445) vs 1.0% (5/485), and the distant recurrence rate was 11.0% (49/445) vs 3.9% (19/445). Of the 79 patients who relapsed, 30.4% (n=24) had achieved a pCR and 69.6% (n=55) had residual disease. The 4-year recurrence risk was 6.9% for patients who achieved pCR versus 12.8% for those who did not (p&lt;0.001). Of the 24 patients who achieved pCR who relapse, 22 (91.7%) occurred within 4 years of diagnosis. Of the 55 patients who did not achieve a pCR who relapse, 48 (87.3%) occurred within 4 years of diagnosis. Among the 19 patients who developed distant recurrence who attained a PCR, the most common first recurrent sites were lung (42.1%), brain (36.8%), and distant lymph nodes (36.1%). Lung and brain metastases occurred in 87.5% and 85.7% within 3years of diagnosis. If pCR was reached, the NAC regimen or HR status did not affect the recurrence-free survival. However, clinical stages II and III at diagnosis (HR (hazard ratio) =35.3 and HR=114.5, p=0.037) were independent predictor of inferior recurrence-free survival in the pCR group. Conclusion Overall, patients who attained a pCR have a better outcome compared to those with residual disease, regardless of hormone status or type of NAC regimen. However, despite achieving pCR after NAC, patients with HER2-positive, clinical stage II/III remain at risk for disease recurrence within 4 years of diagnosis.

Citation Format: Jee Hung Kim, Jii Bum Lee, Soong Joon Bae, Sung Gwe Ahn, Joon Jeong, Min Hwan Kim, Seul-Gi Kim, Gun Min Kim, Jee Ye Kim, Hyung Seok Park, Seho Park, Byeong Woo Park, Seung Il Kim, Joohyuk Sohn. Pattern of recurrence after pathologic complete response after neoadjuvant chemotherapy in patients with early HER2-positive breast cancer: Real-world evidence [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 P2-13-14.