Single center experience with neoadjuvant chemoimmunotherapy versus chemotherapy in patients with high-risk early stage triple negative breast cancer.

e12617 Background: The addition of immunotherapy to neoadjuvant chemotherapy (NAC) has become standard of care for high-risk early-stage triple negative breast cancer (TNBC) after KEYNOTE-522 demonstrated a remarkable pathological response rate (pCR) benefit. Here we conduct a single institution, real world analysis of incorporation of neoadjuvant immune checkpoint inhibitors (ICI) in TNBC. Methods: This retrospective study was conducted by chart review using an IRB approved protocol through Cedars-Sinai Medical Center (CSMC). Inclusion criteria included adults with early stage (I-III) TNBC who were treated with curative intent neoadjuvant chemoimmunotherapy or chemo and completed breast surgery by the data cutoff date 12/31/2024 at CSMC. 173 patients met eligibility criteria. Patient demographics, disease characteristics, treatment variables and clinical outcome were collected. Mann-Whitney test was used for between-group comparisons. Event free survival (EFS) and overall survival (OS) were analyzed by the Kaplan-Meier method. Ninety-five percent confidence intervals were calculated with the Wilson-Brown method. Categorical comparisons used Fischer’s exact test. Toxicity was graded according to CTCAEv.5. Results: Ninety-two patients (53%) received neoadjuvant chemoimmunotherapy (ICI+NAC) while 81 (47%) received NAC alone. Demographics such as race, stage, and BRCA1/2 status between the two groups were similar, but the ICI group was significantly younger (median age of 43 vs. 54 years, p=0.006). Almost all ICI group received platinum-containing NAC, a minority of NAC group did (97% vs 30%, p<0.001). While survival data is still early as Keynote-522 was approved 3 years ago, at two-year follow-up, EFS trends higher in the ICI group (87% [77%-93%]) than in the NAC group (78% [67%-86%]) but not significantly (p=0.18). There was no difference in OS due to paucity of events. Immunotherapies present a unique toxicity profile, but most patients (90%) did not suffer serious (grade 3 or 4) immune related adverse events. Conclusions: This single center analysis showed that adoption of neoadjuvant ICI has led to an increase in platinum use and an improved pCR in early-stage TNBC patients. This study is limited by its sample size, potentially confounded by the increase in platinum use which improves pCR and difference in age of the cohorts. While further longer-term follow-up is needed, these results reinforce the benefits reported in clinical trials. ICI+NAC NAC p-value # of patients 92 81 Median age (years, range) 43 (29-82) 53 (24-85) 0.006 Race White 57% 58% Black 11% 19% Asian 17% 14% Other 15% 10% Stage Stage 1 4% 7% Stage 2 58% 59% Stage 3 38% 33% BRCA1/2 Positive 18% 22% Platinum use 97% 30% <0.001 Anthracycline use 74% 80% pCR rate 60% 43% 0.033 IRAEs (Grade 3 or 4) 10% 0% EFS at 2 years 87% [77%-93%] 78% [67%-86%] 0.18