Changing from Adenocarcinoma to small cells or Neuroendocrine?

Today my dad took blood test and it’s straight that his PSA reduced from 33,2 in 01/03/2022 to 27 on 5 April 2022. He’s taken Zytiga since 10 Mar 2021 with PSA at around 4 and it continuously increased until this weird thing happened. This comparation of PSA is result of blood test’s done at a private hospital while my dad takes cancer treatment at a public hospital as per his insurance scheme where PSA test is done every 3 months and the last done at 25 Feb PSA 33.7 with no change on mets by CT scan).

Does any of you experience or know a case similar to my dad’s? Is it a good sign or not? Can it be Adenocarcinoma turn to small cells or Neuroendocrine? My dad’s bone metastasis when diagnostic of prostate cancer but only recently he feels hurt / uncomfortable at hip and / or leg.

Thank you in advance for your sharing and comments.

[Tall_Allen]

PSA for metastatic PCa is often erratic. I don't know why you think it's NEPC.

[Hidden in reply to Tall_Allen]

Do you mean it’s fluctuation of PSA? I thought PSA fluctuation should be small, not that much

[George71]

If I understood your post -- the PSA s were from 2 different clinics -- that is often the case that they differ slightly.

[Hidden in reply to George71]

No, in the same lab (private hospital). Normally, results at 2 labs are not much different.

[timotur]

I think the concern is whether your father is becoming resistant to Zytiga if his PSA has risen from about 4 to about 33/27 in one year. If he is taking it with Prednisone he may be able to switch to Dexamethazone I believe to extend it's effectiveness. If Zytiga is no longer working then there are follow-on treatments. I don't think NEPC is a concern-- it is hard to characterize, but it sometimes evolves with PSA in single digits with ALP rising beyond the upper normal limit. There are other blood tests that my indicate NEPC such as CR-P. But nevertheless, I would be tracking ALP.

[Hidden in reply to timotur]

He changed to Dexamethasone since 20 october, when psa 25,8. But PSA still continually up with slower speed, and now down strange. Thank for you advice

[LearnAll]

It does not indicate NEPC. Treatment Emergent NEPC occurs after many years of ADT in approx 20% in men with prostate cancer. The sequence is from androgen sensitive to Androgen resistant to eventually Neuroendocrine.To identify NEPC, one has to check S. Chromogranin A, S. Synaptophysin and Neuron specific Enolase. These 3 are blood tests and if they are increasing..it means the PCa is turning into NEPC.

[Hidden in reply to LearnAll]

Appreciate your response, thanks