Abstract PO5-25-04: Predictive value of neutrophil-to-lymphocyte and platelet-to-lymphocyte ratios in patients with triple negative breast cancer treated with pembrolizumab

Abstract Background: Immune checkpoint inhibitors (ICIs) offer new treatment possibilities for women with triple-negative breast cancer (TNBC) – one of the most challenging breast cancer subtypes. The PD-1 inhibitor pembrolizumab (pembro; Keytruda®) is approved in metastatic TNBC (mTNBC) patients with PD-L1(+) tumors, and for neoadjuvant treatment (NAT) in stage II/III TNBC 1, 2. Residual cancer burden (RCB) after NAT is highly prognostic, with pathologic complete response (pCR, RCB 0) anticipating long-term survival 3. In mTNBC, pembro plus chemotherapy in the 1st-line improves progression free survival (PFS), but durable responses are rare. Optimizing ICI use in TNBC thus remains an unmet need, and defining easily assessable markers of response is crucial. Neutrophil-to-lymphocyte ratio (NLR) and platelet-to-lymphocyte ratio (PLR) are peripheral blood surrogates of tumor inflammation and have prognostic and predictive value in TNBC 4-8. Elevated NLR (≥ 5) and PLR (≥ 200) correlate with worse outcomes upon ICIs in melanoma and non-small-cell lung cancer 9, 11-14; however, this has not been studied in breast cancer 9, 10. We evaluated the relationship of baseline NLR and PLR with pembro responses in TNBC patients. Methods: We retrospectively reviewed data from TNBC patients who completed pembro between 10/2/20 - 6/1/23 at Weill Cornell. Patients on NAT who did not complete treatment were excluded. RCB score (pCR/0, 1, 2, 3) was calculated from surgical resection pathology reports using the MD Anderson RCB Calculator 15, 16. Baseline laboratory data were obtained from clinical records. Associations between NLR and PLR with RCB levels were examined using the non-parametric Kruskal-Wallis test (if 2 levels), the Wilcoxon rank sum test (if 2 levels), or the Spearman’s rank correlation. NLR and PLR were also correlated with PFS (measured from pembro start date to date of progression) in metastatic patients. PFS data for metastatic patients without interval imaging since pembro initiation were censored at the date of data analysis, and PFS was not calculated for patients who received only 1 cycle of pembro. Results: We identified 63 eligible patients: 24 were excluded due to lack of TNBC diagnosis (n=20), or because they only received adjuvant pembro (n=4). Of the 39 remaining patients, 5 did not complete NAT and 2 had missing data, leaving 32 evaluable patients (17 in the NAT cohort and 15 in the mTNBC cohort). Overall, the median age was 51 years, and 16% were Hispanic, 11% Asian, 57% non-Hispanic, 24% Black, and 65% Non-Black. Neoadjuvant cohort: The pCR rate was 30%. Patients with both NLR ≥ 5 and PLR ≥ 200, had a pCR rate of 0%; in patients with NLR 5 or PLR 200, pCR rate was 43%. Median NLR in pCR vs. non-pCR groups was 1.91 IQR: 1.72- 2.73 vs. 2.44 IQR: 1.97- 5.24 (p=0.3), with trends towards significance when NLR was compared between RCB levels 1 (2.67; IQR: 2.05, 6.49) vs. RCB levels ≤1 (1.91; IQR: 1.63, 2.58) (p=0.14). Mean PLR was higher in patients with RCB 2-3 (409) compared to those with pCR or RCB 1 (167) (p=0.146). Metastatic cohort: The overall mean PFS was 7.8 months. Visceral metastases were seen in 80% of patients (17% liver, 33% brain). In patients with brain mets, baseline NLR and PLR were higher than in the overall cohort (NLR, 4.86 vs. 2.78; PLR, 429 vs. 186). Conclusions: Our study is the first to evaluate NLR and PLR as response biomarkers in TNBC patients receiving pembro and is the first report of our real-world data of TNBC patients on pembro. In our neoadjuvant cohort, higher baseline NLR and PLR correlated with higher RCB levels, with a trend towards statistical significance. Further investigation and correlation of NLR and PLR with tumor microenvironment features will help to clarify these relationships. Citation Format: Ashley Schreier, Roberta Zappasodi, Inna Serganova, Laura Munoz Arcos, Xi Kathy Zhou, Massimo Cristofanilli, Eleni Andreopolu. Predictive value of neutrophil-to-lymphocyte and platelet-to-lymphocyte ratios in patients with triple negative breast cancer treated with pembrolizumab abstract. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO5-25-04.