I just finished reading Gatenby (2004). To very briefly summarize, some information is lost or transformed to promote cancer cell fitness, while other information is maintained or increased to keep the cell alive. This is just as SJS described using Venn Diagrams in the progenitor thread.
There is no mention of “Functional Information” in this article, only standard Information Theory measures: Shannon, Fisher, mutual, relative entropy (Kullback–Leibler divergence).