Key Clinical MessageTo overcome patient‐initiated treatment refusal because of fear of experiencing severe negative adverse events, mild immunotherapy using a cancer vaccine such as the autologous formalin‐fixed tumor vaccine should be considered.AbstractA patient who refused chemotherapy and immune checkpoint inhibitor treatment for Stage IV uterine cancer after displaying circulating tumor cells and high microsatellite instability received monotherapy with autologous formalin‐fixed tumor vaccine (AFTV). Following treatment, we observed regression of multiple lung metastases, suggesting that AFTV is an attractive treatment option.