Outcomes After Intratumoral Delivery of Immunotherapy in Breast Cancer

BACKGROUND: Immunotherapy is a growing treatment option for challenging breast cancer (BC) subtypes. Systemic administration can have significant adverse events (AEs), prompting interest in intratumoral injection. We evaluated the safety and feasibility of intratumoral injections at our institution. METHODS: This is an IRB-approved retrospective review of neoadjuvant patients who received intratumoral talimogene laherparepvec (TVEC) (NCT02779855) for triple negative breast cancer (TNBC), dendritic cells (DC1) for HER2+ (NCT05325632), HER2 + /ER- (NCT03387553), or TNBC (NCT05504707), or Voyager V1 virus (VV1) (NCT01042379) for high-risk lesions on ISPY2. This study outlines the safety and feasibility of intratumoral injections assessed by AEs, adherence to therapy, and ultrasound guidance. RESULTS: The study included 111 female patients (mean age 51; range 26-80). Forty-seven (42.3%) received TVEC, 62 (55.9%) received DC1, and 2 (1.8%) received VV1. Three patients missed one injection; 110 patients had ultrasound-guided injections. Mean neoadjuvant therapy length was 172 days (range 127-244). Local AEs included pain (20.7%), injection site reaction (27.9%), and hematoma (5.4%). Systemic AEs were reported more frequently, most commonly chills (52.3%), headache (39.6%), and fever (36.8%). DISCUSSION: Intratumoral IT injection is a viable treatment option that may minimize systemic exposure while maintaining therapeutic efficacy. Breast surgeons can play a role in intratumoral IT in BC.