An estimate is made of a time since a given presenting cancer would have first been detectable using a known diagnostic technique, and an estimate is also made of initial characteristics of the given presenting cancer at the time when it would have first been detectable using the known diagnostic technique. A first probability of the cancer being present in a first set of one or more clinically significant remote sites is determined based on the estimated initial characteristics. A second probability of the cancer being present in the first set of one or more clinically significant remote sites is determined based on actual current characteristics of the given presenting cancer. The first and second probabilities are used to estimate incremental risk of incurring presence of the cancer at the first set of one or more clinically significant remote sites by delaying therapy for a unit time