Abstract P4-07-21: Neo-adjuvant chemotherapy in various breast cancer subtypes in the 21st century
Authors: Ananthula Aneesha , Thomas Katharine , Chen Lily , Carey Vincent K. , Sullivan Caitlin M. , Martin Karla M. , Baas Emily , Plasko Kara C. , Sun Brandi , Lanza Madison , Nguyen Cindy , Chapple Andrew , Loch Michelle M. 
Published: March 2023

Introduction Breast cancer is a complex, heterogeneous disease encompassing a spectrum of subtypes with distinct biological features, each having unique responses to various treatment modalities and different clinical outcomes. The type of neoadjuvant chemotherapy (NAC) for locally advanced breast cancer is decided based on breast cancer subtype, which includes triple negative breast cancer (TNBC), hormone receptor positive breast cancer (HR+BC), HER2+ breast cancer (HER2+BC) and triple positive breast cancer (TPBC). Multiple NAC regimens exist but have not been directly compared to determine the optimal treatment regimen in patients with various stages (I-III) and subtypes of breast cancer. The objective of this study was to assess pathological complete response (pCR) rates in patients treated with various types of NAC and analyze associated clinical factors in our diverse patient population.

Methods This study included 297 patients treated with NAC for breast cancer between 2015 and 2021 at LCMC Heath, New Orleans, Louisiana. The tumor, lymph node, metastasis (TNM) system was used for clinical and pathological staging. Biologic subclassification using estrogen receptor (ER), progesterone receptor (PR), HER2 were performed. Response to NAC was documented as pCR when there was no evidence of residual invasive tumor in the breast or axillary lymph nodes. Categorical variables were summarized by reporting counts and percentages, while continuous variables were summarized by reporting means and standard deviations. Fisher exact tests were used to compare pCR status by each chemotherapy status or demographic factor. Wilcoxon Rank-sum tests were used to compare continuous variables across pCR groups. Multivariable linear regression was performed to predict overall tumor shrinkage %.

Results Among all patients, median age was 54.75 years (min-max: 22-78). 30 (10%) patients were stage I, 175 (58.9%) were stage II, 89 (29.9%) were stage III and 3 (1%) were stage IV with oligometastatic disease. 171 (57.6%) were African American (AA), 82 (27.6%) were Caucasians and 41(13.8%) were other race. Table 1. shows chemotherapy and pCR rates among different breast cancer subtypes. Patients with carboplatin (57.3 vs 35.3; p&lt; 0.001), had a higher likelihood of complete remission than non-users. After multivariable linear regression adjustment, Paclitaxel increased the % reduction in tumor size significantly (EST= 39%, CI 2% – 77%; p=0.042) compared to non-users. In the subset of TNBC patients this held in terms of pCR rates (47.1% vs 25%, p=0.036). In TPBC, pCR was higher in younger (p=0.028) and non-AA (p=0.0023) patients.

Conclusion Multiple NAC regimens for breast cancer exist and optimization of regimens is key. We explored the use of several different chemotherapy agents and found the use of carboplatin beneficial, while doxorubicin, cyclophosphamide and cisplatin had a decreased likelihood of achieving a pCR; however, this may be due to the intrinsic nature of the subtypes that would be treated with these NAC regimens. We plan to explore by subtype and treatment regimen in future analysis.Interestingly, AA have significantly less pCR in TPBC, compared to non-AA, although this finding was not seen in other subtypes. Future studies are needed to investigate this further.

Table 1: Chemotheraphy and pCR rates among different breast cancer subtypes.

Citation Format: Aneesha Ananthula, Katharine Thomas, Lily Chen, Vincent K. Carey, Caitlin M. Sullivan, Karla M. Martin, Emily Baas, Kara C. Plasko, Brandi Sun, Madison Lanza, Cindy Nguyen, Andrew Chapple, Michelle M. Loch. Neo-adjuvant chemotherapy in various breast cancer subtypes in the 21st century. [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 P4-07-21.