Real-world use of carboplatin-containing chemotherapy in early triple negative breast cancer (TNBC).

e23285 Background: TNBC is associated with clinically aggressive behavior, limited treatment options, and worse outcomes. Chemotherapy (chemo) guidelines have evolved with regards to the role of carboplatin (carbo), which has shown survival benefit but also increased toxicity and treatment (tmt) delays/discontinuation. We report tmt patterns and uptake of carbo in a large sample of real-world TNBC patients (pts). Methods: We utilized data from the Greater Plains Collaborative (GPC), a PCORnet-funded Clinical Research Network. Under GPC governance and oversight, electronic health records (EHR) from member sites are extracted, transformed and linked with their North American Association of Central Cancer Registries (NAACCR)-formatted hospital cancer registry data. Following a federally funded, IRB-approved protocol, we identified adult female pts diagnosed (dx) between 2014-2022 with first, primary, stage I-III TNBC, initiating chemo within 4 months of dx (neoadjuvant) or surgery (adjuvant only) within 10 academic healthcare systems of GPC. Drug codes and administration dates were extracted from EHR data to identify carbo and neoadjuvant carbo/taxane (NT) with or without doxorubicin/cyclophosphamide (AC). Multivariable logistic regressions controlling for age, stage, grade, race, BMI, and Charlson comorbidity index (CCI: 0, 1, 2+) were used to predict factors associated with use of carbo (model 1) and NT+AC v NT (model 2). Results: Of the 2254 TNBC pts, 31%, 44%, and 25% presented with stage I, II and III disease. Median age and BMI was 55 and 29. 15% was black, 61% had no comorbidity, and 74% received neoadjuvant chemo. Overall, 906 (40%) received carbo, increasing from 25% in 2014 to 71% in 2022. 32%, 81% and 92% of stage I, II, and III pts received carbo in 2022. Uptake of pembro was swift, increasing from 4% of NT and 15% of NT+AC pts in 2020, to 71% (NT) and 87% (NT+AC) in 2022. On multivariate analysis, carbo use was associated with stage (OR = 0.29, 95%CI 0.22-0.37 for stage I v II, and OR = 1.79, 95%CI 1.42-2.26 for stage III v II), grade (OR = 1.35, 95%CI 1.04-1.77 for grade 3 v 1-2), and age (OR = 0.97, 95%CI 0.96-0.98). NT+AC (54%) and NT (40%) were the most common carbo-containing regimen. On multivariate analysis, NT+AC (v NT) was associated with comorbidity (OR = 0.53, 95%CI 0.29-0.95 for CCI of 1 vs 0, and OR = 0.53, 95%CI 0.29-0.98 for CCI of 2+ v 0), stage III v II (OR = 1.74, 95%CI 1.04-2.96) and age (OR = 0.92, 95%CI 0.90-0.94). Conclusions: Guidelines have changed dramatically for TNBC. Only variables of risk (higher stage and grade) predicted carbo use. In contrast, both variables of risk and toxicity (lower comorbidity burden and younger age) predicted intensity of carbo therapy (NT+AC v NT). The variation in treatment patterns and uptake across pts and time in real-world practice illustrate the difficulty in treating aggressive disease with powerful and toxic chemotherapy.