How early can PSA doubling times tell what?

A new study from a group at Duke University has attempted to assess whether data based on PSA doubling times in men with PSA levels up to 0.2 ng/ml can be used as effectively to make early treatment decisions for men with a rising PSA after first-line therapy as can PSA doubling times for men with PSA levels higher than 0.2 ng/ml.

We know that after radical prostatectomy a short “standard” PSA doubling time (PSADT), calculated using PSA values of ≥ 0.2 ng/ml after biochemical recurrence, tends to imply a poor prognosis and a poor response to salvage treatment. Teeter et al. set out to determine whether the so-called early prostate-specific antigen doubling time (ePSADT), calculated from the first detectable PSA level after radical prostatectomy (RP) to the first PSA level ≥ 0.2 ng/ml,  correlated with “standard” PSA doubling times (PSADT).

They based their analysis on data from 157 men in the Shared Equal Access Regional Cancer Hospital (SEARCH) database who had a radical prostatectomy between 1988 and 2005 and had a calculable ePSADT and PSADT values. They used the available data to assess the positive and negative predictive values (PPV and NPV, respectively) of ePSADT and PSADT as methods to project aggressive recurrence (PSADT of < 9 months).

Their resulst showed the following:

  • ePSADT was significantly, though poorly, correlated with PSADT (r = 0.30, P < 0.001).
  • ePSADT more accurately predicted PSADT among men with a long ePSADT.
  • In men with an ePSADT of ≥  20 or ≥ 15 months, the NPV for an aggressive recurrence was 98 and 93 percent, respectively.
  • In men with an ePSADT of < 3 months, the PPV for aggressive recurrence was only 39 percent.

In other words, ePSADT is very good at projecting that a recurring cancer is not aggressive if the ePSADT is > 15 months, but it is not so good at projecting that a recurring cancer is aggressive if the ePSADY is < 3 months.

The authors conclude that a long ePSADT correlated well with a long PSADT and is thus useful in identifying men with prostate cancer recurrence who are at low risk for prostate cancer-specific mortality very early after their initial recurrence. The implication is that, taking other factors into accont, these men may not need immediate salvage therapy, and can delay further action for a signifciant period of time.

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