Survival curves for patients with or without increased IgG responses after PPV. a-f) IgG boosting was a significant prognostic factor for OS and PFS in HER2-positive patients, whereas there was no significant difference between increased IgG responses and these prognoses in mrTNBC and luminal/HER2-negative patients. a, b) mrTNBC: PFS and OS, P = 0.274 and P = 0.152, respectively. c, d) luminal/HER2-negative type: PFS and OS, P = 0.732 and P = 0.571, respectively. e, f) HER2-positive type: PFS and OS, P = 0.0001 and P = 0.001, respectively. HER2, human epidermal growth factor receptor 2; IgG, immunoglobulin G; mrTNBC, metastatic recurrent triple negative breast cancer; OS, overall survival; PFS, progression-free survival; PPV, personalized peptide vaccination.