Abstract PO5-03-11: Ultra-low dose nivolumab added to dose-dense, cisplatin-based neoadjuvant chemotherapy in locally advanced, borderline operable triple negative breast cancer: A matched case-control study

Abstract Background In India, the majority of patients with triple negative breast cancer(TNBC) present with locally advanced and often inoperable disease due to lack of screening, awareness, and social stigma. This makes pathological complete response(pCR) after neoadjuvant chemotherapy(NAC) less likely, leading to early recurrence and poor survival outcomes. Immune checkpoint inhibitors(ICI) in addition to platinum agents have improved both pCR and disease-free survival(DFS). However, these are accessible only to a very small proportion( 3%) of patients in LMICs due to exorbitant costs. The activity and cost-effectiveness of low dose ICI has been demonstrated in head and neck. The efficacy of low dose ICI in the neoadjuvant setting for TNBC has not been studied. We examined our outcomes with ultra-low dose nivolumab( 0.6 mg/kg every 2 weeks) added to NAC for locally advanced and borderline operable TNBC. Methods A retrospective analysis of 132 patients with TNBC who received NAC with the ddDCEP regimen(Docetaxel 75mg/m2 and Cyclophosphamide 600 mg/m2 alternating with Epirubicin 90mg/m2 and Cisplatin 60mg/m2 every 2 weeks for 8 cycles) or ddDCEP plus low dose nivolumab( 0.6mg/kg/2 weeks) and underwent mastectomy at our centre between 2018-2023 was carried out. 105 and 27 patients received ddDCEP alone and ddDCEP + low dose nivolumab respectively. Using rigorous exact matching, 26 matched pairs(52 patients) were obtained based on tumour grade and AJCC TNM stage. pCR in the surgical specimen was the principal outcome assessed. Survival data, adverse events and cost were also analysed. Results The median age of cases and controls was 42 and 40 years respectively. Tumour histology was ductal carcinoma most patients. Across both groups the stage distribution was the same with nearly 85% stage III(IA 3.8%;IIB 7.7%; IIIA 23.1%;IIIB 43.2%;IIIC 19.2%). 92% of cases and 85% of controls had node positive disease. 62% of cases and 46% of controls had T4 disease. At a median follow up of 9 months, there were no recurrences or deaths among the cases. The most common immune mediated adverse event was hypothyroidism seen in 11.5% of cases. The rates of grade 3/4 anaemia, thrombocytopenia and febrile neutropenia were approximately 38%, 10% and 3.8% across cases and controls respectively. The median dose of nivolumab was 0.27mg/kg/2weeks as opposed to the approved dose of 3mg/kg/2weeks for most indications. The range of doses varied from 0.07 to 0.58mg/kg/2weeks. In the overall cohort, the addition of nivolumab did not have any apparent effect on the pCR rates which were identical at 42.3% in both cases and controls. However, there was a positive correlation between the total dose of nivolumab/kg(body weight) and the likelihood of pCR(coefficient 0.34; p-value 0.046). Patients who received higher than the median dose of nivolumab had a significantly higher likelihood of attaining pCR than those who received lower doses (69.2% pCR vs.15.4%;p-value 0.015). The cost of nivolumab at 0.6 mg/kg for 4 doses is approximately USD2000 compared to USD34400 for 8 doses of pembrolizumab in the neoadjuvant component of the KEYNOTE-522 regimen. Conclusion In this cohort with locally advanced/inoperable TNBC, the addition of ultra-low dose nivolumab did not improve pCR overall compared to a matched control set who did not receive ICI. However, in the subset of patients who received between 0.27-0.58 mg/kg/2weeks, the pCR rates were significantly higher at 69%. This presents a promising and cost-effective approach for TNBC management in LMICs. This effect needs verification in larger phase II/III trials. Table. Citation Format: Zachariah Thomas, Josh Georgy, Ashish Singh, Anjana Joel, Divya Thumaty, Ajoy John, Jerryes Wisely, Grace Rebekah, Elanthenral Sigamani, Anish Cherian, Deepak Abraham, Paul Jacob, Rajesh Balakrishnan, Patricia Solomon, Selvamani Backianathan, Raju Chacko. Ultra-low dose nivolumab added to dose-dense, cisplatin-based neoadjuvant chemotherapy in locally advanced, borderline operable triple negative breast cancer: A matched case-control study 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 PO5-03-11.