Spatiotemporal Fluctuation Induced Transition in a Tumor Model with   Immune Surveillance
  We report on a simple model of spatial extend anti-tumor system with a fluctuation in growth rate, which can undergo a nonequilibrium phase transition. Three states as excited, sub-excited and non-excited states of a tumor are defined to describe its growth. The multiplicative noise is found to be double-face: The positive effect on a non-excited tumor and the negative effect on an excited tumor. 
Wei-Rong Zhong, Yuan-Zhi Shao, Zhen-Hui He