Table 2.

Pretreatment PSA Doubling Time Values Using Different Intervals in the Calculation and Ratio of PSA Doubling Times

PSA doubling time was calculated using the log slope method.¹⁴ Briefly, the PSA rate variable was calculated by taking the natural log of each PSA measurement, plotting them versus time and then measuring the slope of the linear regression through the data points ln [PSA_t]=ln [PSA_initial]+mt (t=time). PSADT was then calculated by dividing ln 2 by m.¹⁴ PSADT1, PSA doubling time calculated using the conventional interval from the first rise greater than the nadir during androgen deprivation therapy until the start of the next treatment; PSADT2, PSA doubling time calculated using the period from the initial rise after anti-androgen withdrawal until the start of chemotherapy; PSADT3, PSA doubling time calculated using the total period from the first rise greater than the nadir during androgen deprivation therapy until the start of chemotherapy; PSADT2/PSADT1, the ratio of PSADT2 to PSADT1; SD, standard deviation; PSA, prostate-specific antigen.