The feasibility of using an autologous GM-CSF-secreting breast cancer vaccine to induce immunity in patients with stage II-III and metastatic breast cancers

Purpose The antigenic targets of immunity and the role of vaccination in breast cancer are unknown. We performed a phase I study of an autologous GM-CSF-secreting breast cancer vaccine in patients with metastatic and stage II-III breast cancer. Methods Tumor cells from patients with metastatic (n = 15) and stage II-III (n = 7) disease were transduced with a replication-defective adenoviral vector encoding GM-CSF, and then irradiated. Twelve and seven patients with metastatic and stage II-III disease, respectively, received weekly vaccination for three weeks, followed by every other week until disease progression or vaccine supply was exhausted (metastatic) or until six total vaccine doses were administered (stage II-III). Results Among those patients with metastatic disease who received vaccinations, eight had progressive disease at two months, three had stable disease for 4-13 months, and one has had no evidence of disease for 13 years. Of the patients with stage II-III disease, five died of metastatic disease between 1.16 and 8.49 years after the start of vaccinations (median 6.24 years) and two are alive as of September 2021. Toxicities included injection site reactions, fatigue, fever, upper respiratory symptoms, joint pain, nausea, and edema. Four of five evaluable patients with metastatic disease developed a skin reaction with immune cell infiltration after the fifth injection of unmodified, irradiated tumor cells. Conclusion We conclude that tumor cells can be harvested from patients with metastatic or stage II-III breast cancer to prepare autologous GM-CSF-secreting vaccines that induce coordinated immune responses with limited toxicity.