Abstract P2-16-25: Young age breast cancer who achieve pathologic complete response after neoadjuvant chemotherapy display excellent outcome than older age breast cancers
Authors: Lee Young Joo , Shin Yung Il , Kim Jisun , Lee Sae Byul , Kim Hee Jeoung , Chung Il Yong , Ko Beom Seok , Lee Jong Won , Son Byung Ho , Ahn Sei-Hyun 
Published: March 2020

Abstract
Introduction: Patients with pathologic complete response (pCR) after neoadjuvant chemotherapy (NCT) is known to have a good prognosis compared with patients with no residual disease necessitating additional adjuvant systemic therapy for some population. Also there are cases of recurrence and/or death among patients with pCR. We aimed to 1)analyze whether prognostic impact of pCR differ across subtypes and age groups and 2)investigate factors associated with outcome after achieving pCR.
Methods: Among 1930 patients who underwent NCT at Asan Medical Center between 1890 to 2018, 1688 patients with clinico-pathological, follow-up data available were analyzed. 339 (20.1%) patients had pCR defined as ypT0/Tis with no residual nodes(N0) after NCT. Pathologic CR rate were 10.2% (102/1003), 40.0% (100/250) and 31.6% (137/434) in each HR positive, HRneg/HER2pos and triple negative tumors. Pathologic CR rate were 19.7% (232/1175) and 20.9% (107/513) in young age and old age group respectively.
Results: Median follow up period was 62 months (6-129 months). Five-year disease free survival (5yr-DFS) of ‘total’ patients and patients with ‘no-pCR’ and ‘pCR’ were 81.7%, 79.1% and 92.4% respectively (p=&lt;0.01). Pathologic complete response was significant favorable indicator across all subtypes and both in young/old age group (Cox regression analysis in each group, Table 1).
Among patients with pCR, residual in-situ disease (p=&lt;0.01, HR 3.889), tumor size&gt;5cm (p=0.006, HR=1.45), and negative hormone receptor (p&lt;0.01, HR=9.269) were independently associated with worse disease free survival. These prognostic factors were similar in patients with residual disease as well.
Intriguingly, magnitude of impact affecting prognosis differed by age groups that younger patients
(≤50) who achieved pCR displayed excellent outcome similar to older age group (HR=1.33, CI 0.57-3.12, p=0.51). On the other hand, young age patients who did not achieve pCR had the worst outcome with 5yr-DFS 77.3% indicating the necessity of additional systemic therapy. Also, while HR negative tumors are known to have worse outcome, HRneg/pCR group had longer 5yr-DFS than HRpos/no-pCR groups (90.6% vs 83.9%, p=0.009). The outcomes were similarly observed for overall survival analysis.
Conclusion: Patients with pCR after NCT showed better DFS and OS across all subtypes. Achieving pathologic complete response was a good prognostic indicator especially in young age population. Younger patients with residual disease after NCT may be candidates for additional adjuvant systemic therapy after surgery.
Table1. Cox regression analysis in each grouppCRNo-pCRHazard ratio (ref, pCR)95%CIP value5yr-DFS (%)5yr-DFS (%)SubtypesHR positive96.183.93.081.35-7.020.007HRneg/HER2pos89.672.02.431.13-5.220.023HRneg/HER2pos91.567.83.591.87-6.89&lt;0.001AgeYoung age (≤50)93.377.34.502.53-8.08&lt;0.001Old age (&gt;50)90.183.42.251.06-4.750.033
Citation Format: Young Joo Lee, Yung Il Shin, Jisun Kim, Sae Byul Lee, Hee Jeoung Kim, Il Yong Chung, Beom Seok Ko, Jong Won Lee, Byung Ho Son, Sei-Hyun Ahn. Young age breast cancer who achieve pathologic complete response after neoadjuvant chemotherapy display excellent outcome than older age breast cancers [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 P2-16-25.