Since the development of the radiating electron theory by P. A.M. Dirac in 1938 [P. A.M. Dirac, Proc. R. Soc. Lond. A 167, 148 (1938)], many authors have tried to reformulate this model, called the “radiation reaction”. Recently, this equation has become important for ultra-intense laser–electron (plasma) interactions. In our recent research, we found a stabilized model of the radiation reaction in quantum vacuum [K. Seto et al., Prog. Theor. Exp. Phys. 2014, 043A01
(2014)]. It led us to an updated Fletcher–Millikan charge-to-mass ratio including radiation. In this paper, I will discuss the generalization of our previous model and the new equation of motion with the radiation reaction in quantum vacuum via photon–photon scatterings and also introduce the new tensor dEμναβ/dm, as the anisotropy of the charge-to-mass ratio.