Definitions for "Doubling time"
the time that it takes a value (like PSA) to double
The time required for a cell to double in number. Breast cancer has been shown to double in size every 23 to 209 days. It would take one cell, doubling every 100 days, eight to ten years to reach one centimeter, 3/8 inch.
The time needed for a population to double. See also generation time.