Does a change in CA19-9 indicate change in tumor?

is there a formula which converts % change in CA19-9 values to change in tumor dimensions?
For example: if the difference between two CA19-9 readings is a 20% increase, does that mean the tumor increased by 20% over the same time period?
is there anyway to determine the rate of change in tumor dimensions? in other words, did the tumor change happen linearly, exponentially or logarithmically?

math was a long time ago, so thanks for any explanations