What is the accuracy of an immediate PSM PET scan after SBRT Treatment ?

[God_Loves_Me]

I finished my SBRT Treatment, and now MO ordered a PSMA PET scan that's less than one week. What's the accuracy of a PSMA PET Scan immediately after SBRT treatment?

[LearnAll]

God Loves You....I do not think anything will be much diferent if PSMA PET CT is ordered just 1 week after SBRT. To understand it better..lets first know how SBRT (Steriotactic body radiotherapy) works.. A bunch of x ray beams are sent towards a metastatic spot. This is done via a very high tech radiation machine (True beam or Cyberknife) Now, these beams of x ray converge and form a cone..eventually reaching a very high velocity very pointed "super bean" which hits the metastatic spot. This causes severe injury to cancer cells breaking their DNA strands. Cancer cells stay alive for a while but they are severely crippled. Slowly overweeks and months these crippled cells start dying and crippled cell also lose their capacity to reproduce slowing tumor growth. The dead cells while busting and dying, release substances which attract all kind of natural killer cells, phagocytes, macrophases...they all start munching on cancer cells in the area. Some neiboring cells die just due to fear watching their fellow cancer cells DNA cracking and breaking...This interesting phenomenon is called "Abscopal Effect" Because cancer killing effect of SBRT is a very slow process, you might see changes in PSMA PET-CT and /or PSA in many months sometimes in 2 or 3 years. If your pain is gone..its time to rejoice !

[God_Loves_Me in reply to LearnAll]

Thank you agree with all points. I really appreciate your comments

[dhccpa in reply to LearnAll]

Learn all that was damn good writing! I was getting excited at the fear of the neighboring cancer cells watching their compadres die. I'm assuming nearby healthy cells were giggling and applauding! Hell yes!

Carry on...I have missed your contributions!

[Tall_Allen]

It will tell you nothing. It may take years for all the cancer in your prostate to completely go away. Meanwhile, it is effectively dead but still attached to your prostate. It is what I call "zombie cells." It is caused by irreparable damage done to the DNA of your cancer cells. When those cells eventually try to replicate, they can't, and die (called " mitotic catastrophe").

The only way to track progression is by periodic PSA tests. It took me almost 4 years to reach my nadir.

[Cancer2x in reply to Tall_Allen]

Hmmm….“Mitotic Catastrophe”….. what a new, and wonderful, phrase to meditate on!

[j-o-h-n in reply to Cancer2x]

It's "second" cousin Mitotoc..........

Good Luck, Good Health and Good Humor.

j-o-h-n

[God_Loves_Me in reply to Tall_Allen]

Thank you agree with all points. I really appreciate your comments

[Bamagrad in reply to Tall_Allen]

Tall Allen, Is there a reason everyone is on Xtandi rather than Nubeqa?

[God_Loves_Me in reply to Bamagrad]

I asked 4 MO and nobody able to explain difference between Xtandi and Nubeqa

[Bamagrad in reply to God_Loves_Me]

My husband was on nubeqa and lupron. Had mets to lymph nodes in neck with uptake noted in torso. Briefly put on taxotere, stopped nubeqa, but continued lupron for three chemo treatments. Stopped chemo to begin Pluvicto (studies show it may work better pre-chemo). After two Pluvicto treatments his PSA is doubling rapidly. 14 to 27 to 77. Asked why he is bot concurrently taking Zytiga and doc said bc of side effects and he became mCRPC on Nubeqa. Thoughts? (Sorry, I dont have a bio as wasn’t familiar with terminology. He was diagnosed with localized, aggressive prostate cancer in July 2020 Nd had radiation. At same time, they found head and neck cancer, diagnosed as adeno cystic carcinoma in the base of tongue. Said the rare, 1%. Cancer is NOT related to his prostate cancer. He never smoked and played baseball until he was 52. Tumor was removed from base of tongue along with partial glossectomy and since 2020 he has been battling his prostate cancer.)

[God_Loves_Me in reply to Bamagrad]

What's his medicine right now ?

[Bamagrad in reply to God_Loves_Me]

Lupron and Pluvicto only. Since 2020 he has has radiation for local prostate cancer, Nubeqa, Lupron and provenge.

[Tall_Allen in reply to Bamagrad]

Nubeqa is approved with docetaxel for newly diagnosed metastatic PCa and for non-metastatic CRPC. Xtandi is approved for newly diagnosed metastatic PCa, for non-metastatic CRPC, and for metastatic CRPC.

[Bamagrad in reply to Tall_Allen]

Thank you. On this site, it swems most people are taking Xtandi and can somehow get it to start working again. My husband’s testoterone remains very low, but PSA started to rise and is doubling tapidly now that on Pluvicto only. He has has PSMA PET Scan as well as CT scans. Scheduled for PET scan today aince his psa was 77 last week -the highest it has ever been. Just wondering if he should add zytiga or Nubeqa?

[Tall_Allen in reply to Bamagrad]

They tried combining Zytiga and Xtandi. It didn't provide any benefit more than Zytiga alone - it just increased side effects.

[God_Loves_Me in reply to Bamagrad]

Hey I hope you know while on Pluvicto, PSA number can be confusing. SCAN are more reliable source. Specially compare scan before Pluvicto treatment , during Pluvicto and after Pluvicto treatment.

[Bamagrad in reply to God_Loves_Me]

Good to know. He had psma Pet yesterday and we are waiting to hear.

[janebob99]

I looked at your bio, and you didn't mention having a previous PSMA-PET scan before SBRT. Perhaps the RO wants to do a PSMA-PET scan to check if he or she missed any other spots after completing SBRT? Perhaps it's a Cover-Your-Ass kind of thing?

I don't know if freshly-irradiated PCa cells can still uptake the ligand agent molecules that bind to PSMA sites or not. If they can't bind to the ligand agent, then the PSMA-PET Scan won't show those irradiated spots. In that case, only un-irradiated spots that still have live PCa cells will light up.

Remember that PSMA-PET scan can't detect small spots of cancer. They have to be a minimum size before being detectable.

On the other hand, if freshly-irradiated PCa cells still have active PSMA sites on them, then a PSMA-PET scan done right after SBRT would show the very same hot spots as one done just before doing SBRT, and it will be a waste of time and money.

Let us know what you find out.

[God_Loves_Me in reply to janebob99]

Thank you agree with all points. I really appreciate your comments