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PSA doubling time calculator differences
I just got my recent PSA results today. 12/22/2025 PSA 1.29 on 11/03/2025 PSA was 0.35.
I entered that information on the Sloan Kettering PSA doubling time calculator. The result was a doubling time of 0.9 months.
I entered the exact same information on he Omni PSA calculator and it said the doubling time was 0.56 months.
I am wondering why the were not the same? Is there a "best" calculator to use?
It really may not be relevant because they both indicate a very rapid doubling time. I have been on a treatment holiday for about 7 months. In that time my PSA has gone from 0.01 (04/25/2025) to 1.29. So my treatment holiday will be ending soon...
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Can't help with an answer but following to learn. Thanks for asking the question!
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2 ReactionsMine came out as a negative on both sites...
-31.1 months.
What does that mean?
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1 ReactionThough there are two or three core methods that are generally used for calculating PSADT, there are over 20 methods for calculating PSADT due to various factors like assay differences and data selection, leading to different results.
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3 Reactions@harry100
Were both exactly the same results? I have never heard of a negative doubling time.
@harry100 If your PSADT was negative, that simply means that your PSA decreased during the period you’re measuring.
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2 ReactionsYour PSA went up 2.7 times in 1.5 months. That is a very fast doubling rate. The ,56 Sounds closer to reality. In either case, the Doubling rate is less than one month.
You should speak to the doctor about this, Waiting one more month for a test may make sense, but that is a ,94 Increase in 1.5 months which is significant.
Sounds like you need to go back on ADT, Let your doctor discuss this with you.
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6 ReactionsYou should try to get a PSMA pet test as soon as possible. There may be a visible metastasis that can be zapped so you can stay off the drugs.
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4 Reactions@jeffmarc
Thank you Jeff. I have contacted my oncologist regarding this. At my last visit we discussed when to restart treatments. I am oliometastatic. I have only had one metastasis in my five years of treatment and that was to a lymph node in my chest. That only showed up on the PET/CT when my PSA rose to 6.56. I've had 6 PSMA PET scansin the 5 years of treatment. Last year my PSA went up to 10.56 went I was on my last treatment holiday and there were no metastasis found. Because of that we decided that once my PSA rose to 5 or above there would be another PET/CT and then we will restart the ADT. (at this rate that could be in a few weeks). At the next Ancan Advanced PC group I will probably give an update and see what others have to say. Thanks for all you do here and there to help!
The 0.9 month doubling (i.e., your PSA increased by 90% over a 30-day single month) seems to be a fairly accurate calculation for your 11/03/2025 to 12/22/2025 50-day testing period.
Another way to look at this would be to consider your 11/03/2025 to 12/22/2025 testing period being slightly less than two months. During this period your PSA progressed at a monthly doubling pace of approximately 90%.
I agree with @jeffmarc on this result. Unfortunately this appears to be a very fast PSA doubling rate.
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1 Reaction@aldenrobert
Hello Alden,
Mine went from a PSA 9 in Apr to PSA 7.42 in Dec
They were the same in slope -0.3, but differed slightly in velocity -2.2 vs -2.34
I don't understand all this
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