Abstract P4-07-14: Long-term Outcomes After 1 or 2-3 Lines of Neoadjuvant Therapy in Stage III Inflammatory Breast Cancer

Abstract Background: Inflammatory breast cancer (IBC) is associated with a poor prognosis. While many stage III IBC patients (pts) experience a sufficient response to first-line (1L) neoadjuvant chemotherapy (NAC) to permit subsequent surgical therapy, the prognostic significance of requiring additional NAC to enable resectability is unknown. We sought to describe the pathologic complete response (pCR) rates, breast cancer-free survival (BCFS) and overall survival (OS) among pts requiring 1 vs >1 lines of NAC prior to surgery. Methods: Upon IRB approval, pts with stage III IBC from 2 academic institutions (Dana-Farber Cancer Institute and MD Anderson Cancer Center) who received 1L or 2-3 lines (2-3L) of NAC prior to surgery were identified. Standard NAC regimens containing different drugs, such as AC-T or TCHP, were considered as 1L. Pts with locoregional progression or metastatic disease prior to surgery were excluded. Hormone receptor (HR), HER2 status, grade, and pCR, defined as no residual invasive cancer in the breast and the axilla, were evaluated. BCFS, defined as time from surgery to locoregional and/or distant recurrence, and OS, defined as time from surgery to death, were evaluated by the Kaplan-Meier method. Multivariable Cox models stratified by institution and containing the covariates pCR and tumor subtype were utilized to estimate the HR of 2-3L vs. 1L of therapy. Results: 808 eligible pts diagnosed between 1997 and 2020 were identified. 733 (91%) had 1L and 75 (9%) had 2-3L of NAC, and the median age was 50 years. 295 (37%) had HER2+, 282 (35%) HR+HER2-, 211 (26%) had HR-HER2- disease and for 20 (2%) pts, the receptor status was unknown. The median time from diagnosis to surgery was 6 months. Grade III disease, triple-negative and HER2-positive disease were more prevalent in pts receiving 2-3L of therapy (table). pCR was achieved in 178 (24%) pts receiving 1L of NAC, and in 14 (19%) pts receiving 2-3L of NAC. At 68 months of median follow-up, 417 (52%) pts experienced a recurrence with 376 in the 1L group and 41 in the 2-3L group. The 5-year BCFS was shorter for the 2-3L group compared to the 1L group (33% v 46%, HR=1.37; 95% CI:0.99-1.91). However, in 192 pts with a pCR, BCFS was similar, regardless of the number of NAC lines. There were 38 recurrences among 178 1L pts, and 3 recurrences among 14 2-3L pts, resulting in BCFS of 76% and 83% in 1L and 2-3L pts, respectively. Overall, there were 308 deaths, 276 deaths among 1L pts and 32 among 2-3L pts. The 5-yr OS estimate in 1L versus 2-3L pts was 60% versus 53% (HR=1.32, 95% CI: 0.91-1.93). Conclusion: Among pts with stage III IBC, pCR was observed among 24% who had 1L and 19% of pts who required 2-3L of NAC. BCFS and OS were comparable among pts with pCR after 1L and 2-3L. Our results suggest the need to continue to optimize current treatment strategies in IBC to improve pCR rates across all disease subtypes regardless of the number of lines of NAC required. Citation Format: Faina Nakhlis, Samuel Niman, Naoto T. Ueno, Elizabeth Troll, Sean Ryan, Eren Yeh, Laura Warren, Jennifer Bellon, Beth Harrison, Toshiaki Iwase, H. T. Carisa Le-Petross, Sadia Saleem, Mediget Teshome, Gary J. Whitman, Wendy Woodward, Beth Overmoyer, Sara Tolaney, Meredith Regan, Filipa Lynce, Rachel M. Layman. Long-term Outcomes After 1 or 2-3 Lines of Neoadjuvant Therapy in Stage III Inflammatory Breast Cancer [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P4-07-14.