Does PSA doubling time apply with very low absolute PSA values? My dad's PSA has been slowing climbing since August 2019. 0.01-->0.02-->0.06--0.13 today. Wondering if his treatment needs to be modified. He's currently on Lupron and bicalutamide and received up front docetaxel for 6 rounds.
Thanks
No it doesn't. It is only valid for PSAs over 0.1 and there should be at least 3 of them. That said, I think your dad should discuss advanced hormonal therapy (Zytiga, Erleada or Xtandi) with his oncologist at his next visit.
Hi TA, please understand that I am not doubting you. For my own education I'm wondering if you have a link to a study or studies or a reference doc? Thanks.
PSADT was determined to be a risk factor in the late 1990s when the only PSAs available had a lowest value of 0.1,and they did not calculate PSADT for values less than 0.2, so values lower than that have never been correlated with risk. This is how it was calculated:
"Serum PSA level increases above 0.2 ng/mL demonstrated an exponential growth curve similar to that originally reported by Patel et al.13 By this manner, a correlation between the log of PSA levels and time was linear. Prostate-specific antigen doubling time (PSADT) was calculated by natural log of 2 (0.693) divided by the slope of the relationship between the log of PSA and time of PSA measurement for each patient. To determine the optimal PSADT cutoff for predicting metastatic disease progression for this cohort, several doubling-time calculation models were analyzed. Models that used all postoperative PSA values, only the first 2 values regardless of level,13 only the first 2 values after a level of 0.2 ng/mL was reached, and all PSA values within a 2-, 3-, and 5-year period following a documented PSA elevation were analyzed by recursive partitioning to determine the optimal PSADT cutoff level. The method of recursive partitioning involved calculating PSADT based on the PSA values in all of the above models and using sequential values of PSADT provided by each model as a trial cutoff level to determine the optimal separation of men based on their risk of developing metastatic disease. The PSADT values that were less than 0 (stable, nonincreasing, or decreasing PSA levels) were assigned a value equal to 0. The PSADT values that were exceptionally long (eg, >100 months) were assigned a value of 100 months for ease of calculations."
jamanetwork.com/journals/ja...
RTOG uses this definition:
1. The patient must have a PSA of ≥ 0.2 ng/mL and rising at least 6 weeks after prostatectomy.
Rising means a PSA of < 0.2 and a PSA of ≥ 0.2 ng/mL, a PSA of 0.2 and a PSA > 0.2 ng/mL or a PSA > 0.2 and a further PSA increase.
There must be 3 consecutive detectable PSAs spaced by ≥ 2 month intervals.
2, The lowest value must be 0.1 ng/mL (detectable) or higher (0.15 by hypersensitive assay may be used)
Example: < 0.1, 0.2, 0.3 ng/mL (not enough detectable PSAs, need another value spaced at least 2 mo. from last value);
Example: 0.1, 0.2, 0.3 ng/mL (use all three PSAs);
Example: 0.1, 0.15, 0.2 ng/mL (this is allowed for PSADT calculation technically, but another PSA is encouraged).
The calculation of PSADT in the setting of fluctuating PSAs that go back to 0.1 or less should be calculated from the last value of 0.1 or greater.
Example: 0.2, 0.1, 0.2, 0.1, 0.3, 0.4 ng/mL (use the last 3 PSAs);
Example: 0.1, 0.2, 0.4, 0.2, 0.3, 0.4 ng/mL (use all PSAs since all are ≥ 0.1 ng/mL).
This is how the PSADT working group defined it:
"PSADT is often calculated assuming an exponential rise in serum PSA and first-order kinetics. The formula takes into account the natural logarithm of 2 divided by the slope obtained from fitting a linear regression of the natural log of PSA on time.14 All PSA values used in the calculation should be ≥0.20 ng/ml and follow a rising trend. PSA values need not be consecutively rising and all values obtained over a maximum period of 12 months should be included in the calculation. The maximum period of the past 12 months is recommended to reflect the patient’s current disease activity, since in some men PSADT may change over time. Minimum requirements for the calculation are 3 PSA values obtained over 3 months with a minimum of 4 weeks between measurements. "
ncbi.nlm.nih.gov/pmc/articl...
Thanks!
Do you think it might be worth a shot to stop the bicalutamide and recheck psa? I thought I read somewhere on this site that doing that can sometimes cause the psa to drop? My dad’s oncologist is pretty by the book and doesn’t want to add abiraterone at such a low psa. But with a little bit of extrapolation from what is known about the various cancer treatments, seems reasonable to conclude that earlier is always better/more bang for the buck, at least as it pertains to prostate cancer.
Thanks again for the input.
It's called Bicalutamide Withdrawal Syndrome I think it is worth a try if his oncologist agrees.
If he received upfront docetaxel, he has been diagnosed with metastases, so I don't understand the argument for delaying abiraterone.
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