Metastasis of cancer refers to spread of the disease from one organ to another not directly connected with it.
Cancer kills because of metastasis
The pH of a tumour has been heavily correlated with metastasis. For a cancer cell to get out of the extracellular matrix, or the cells around it, one of the methods it uses is a decreased pH
Experiments shows that nanoparticles can be used to change pH level and thus prevent metastasis i.e. prevent cancer from spreading.