Marieke van Son

156 CHAPTER 8 Model 2 The full regression equation for model 2 is as follows: Or for calculating the predicted survival probability: Where: h(t) = the expected hazard at time t h 0 (t) = the baseline hazard at time t s(t) = the expected survival probability at time t s 0 (t) = thebaselinesurvival at time t (seeTable2 for baselinesurvival at 12, 24, and36months) Age = age in years at time of FS-HDR-BT ln = natural logarithm PSA = pre-salvage PSA level in ng/ml Seminal vesicle involvement = 0 when not applicable, 1 when applicable Time to PSA nadir = post-salvage time to nadir in months %PSA reduction = PSA reduction (ratio between pre-salvage PSA and post-salvage PSA nadir) in % PSADT = PSA doubling time in months PSADT’ can be calculated as follows: