Radiotherapy on bone - how long for PSA to drop? - Advanced or metastatic cancer

User

Posted 04 Nov 2022 at 19:12

Hi folks

Sorry if this has been discussed - please direct me if it has!

A PSMA in July showed one area of bone metastasis, so we decided to have RT on it, 5 sessions. I think I will have a PSA follow-up test after 8 weeks, like I did when I had RT to the prostate bed 6 years ago. Then, the PSA dropped further as time went on, for about a year. I'm told it can take 18 months or so to drop fully. But does this apply if the PCa in bone? It's PCa after all.

If anyone has any experience and/or knowledge of this, I'd be grateful.

Thanks

User

Posted 05 Nov 2022 at 19:46

The RT damages the cells' DNA. Healthy cells can repair their DNA, but in cancer cells the repair mechanism is usually faulty and eventually the damaged cell dies, but it can take months to do so.

Best wishes,

Chris

User

Posted 07 Nov 2022 at 16:52

Originally Posted by: Online Community Member

So your radiotherapy was safe and accurate enough to hit that node? No danger of damaging soft tissue around it?

Yes, of course; modern EBRT can be targeted at one node. There may be a small amount of collateral damage on the route in but the computer programme is written in such a way to minimise this as much as possible.

"Life can only be understood backwards; but it must be lived forwards." Soren Kierkegaard

User

Posted 07 Nov 2022 at 16:56

Originally Posted by: Online Community Member

Would you be able to say why radiotherapy on bone may not always lead to a drop in psa? My logic says that if that particular zone of cancer is destroyed, it won't produce psa anymore.

But I do understand it can take quite a time for cancer cells to fully die etc. Thank you.

I think you have a picture in your head of the tumour being smashed to smithereens by the RT and therefore no longer existing. That isn't what happens - the tumour is still there but the cancer cells have been damaged and won't be able to reproduce. As you still have some cancer in a couple of lymph nodes (and probably in other places that are just not showing up on scans yet) your PSA may not drop a lot even in 18 months' time.

"Life can only be understood backwards; but it must be lived forwards." Soren Kierkegaard

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User

Posted 05 Nov 2022 at 00:04

RT to a bone met doesn't always lead to a significant drop in PSA but if it does, the nadir will be in about 18 months, just as it would have been if the prostate was the target

"Life can only be understood backwards; but it must be lived forwards." Soren Kierkegaard

User

Posted 05 Nov 2022 at 07:18

OK Lyn thank you. But if the scan shows just the one site, and it's destroyed, why might the psa not drop?

Thanks

User

Posted 05 Nov 2022 at 10:55

Because the RT doesn't necessarily kill the prostate cancer stone dead there and then - it fatally injures it and causes a lingering death.

"Life can only be understood backwards; but it must be lived forwards." Soren Kierkegaard

User

Posted 05 Nov 2022 at 12:04

Ah, right...so it takes quite a while to kill them, so it will therefore take quite a while to show a psa level drop....and the psa can actually rise to begin with due to inflammation, I think?

User

Posted 05 Nov 2022 at 16:59

Bailey, did you originally have surgery, I would be interested to see your history of results. I had 5 sessions of SABR treatment to a pelvic tumor in August 2022. A PSA test a six weeks after treatment didn't show a drop but there wasn't a rise. Next test is 26 Jan 2023. Not sure if tumors react the same as bone mets, but I am sure someone will know.

Thanks Chris

User

Posted 05 Nov 2022 at 17:21

Hi Chris

Was the tumour on the pelvic bone, or soft tissue in the pelvic area? So, you had no drop but no rise either. Was that the only major mets you have?

User

Posted 05 Nov 2022 at 18:48

Bailey, sorry , the tumor was / is in a pelvic lymph node. It was certainly the only thing that was detected by the PSMA scan. If you look at my profile there is a list of PSA values.

Thanks Chris

User

Posted 05 Nov 2022 at 19:46

The RT damages the cells' DNA. Healthy cells can repair their DNA, but in cancer cells the repair mechanism is usually faulty and eventually the damaged cell dies, but it can take months to do so.

Best wishes,

Chris

User

Posted 07 Nov 2022 at 12:03

Would you be able to say why radiotherapy on bone may not always lead to a drop in psa? My logic says that if that particular zone of cancer is destroyed, it won't produce psa anymore.

But I do understand it can take quite a time for cancer cells to fully die etc. Thank you. Lyn are you able to help me here? Thanks!

Edited by member 07 Nov 2022 at 16:55 | Reason: No reply just yet!

User

Posted 07 Nov 2022 at 13:18

Yes I had surgery 6.5 years ago, then RT 6 years ago. A bit had already escaped, due to no testing being offered in time. Hmm. Just too late. So PSMA scan in July showed 2 to 3 nodes affected, relatively small amount, and this bit on the right sitting bone. So that was targeted and assumed to be producing most of the psa. That area should, now, be destroyed, though I get why it takes months to show that as a reduction in psa.

Edited by member 07 Nov 2022 at 13:49 | Reason: Mistakes

User

Posted 07 Nov 2022 at 15:31

So your radiotherapy was safe and accurate enough to hit that node? No danger of damaging soft tissue around it?

User

Posted 07 Nov 2022 at 16:52

Originally Posted by: Online Community Member

So your radiotherapy was safe and accurate enough to hit that node? No danger of damaging soft tissue around it?

"Life can only be understood backwards; but it must be lived forwards." Soren Kierkegaard

User

Posted 07 Nov 2022 at 16:56

Originally Posted by: Online Community Member

Would you be able to say why radiotherapy on bone may not always lead to a drop in psa? My logic says that if that particular zone of cancer is destroyed, it won't produce psa anymore.

But I do understand it can take quite a time for cancer cells to fully die etc. Thank you.

"Life can only be understood backwards; but it must be lived forwards." Soren Kierkegaard

User

Posted 07 Nov 2022 at 17:54

Originally Posted by: Online Community Member

So your radiotherapy was safe and accurate enough to hit that node? No danger of damaging soft tissue around it?

Bailey, I was warned of possible side effects, but was also told it wasn't that close to the bladder or bowel. Salvage RT did major damage to my bladder and I now have a permanent suprapubic catheter.

Thanks Chris

User

Posted 07 Nov 2022 at 18:46

Oh, right, so you had radiotherapy to the prostate bed, and later the radiotherapy targeted at the node. Good that went OK. I have some nodes affected, so I'm keen to explore the possibility of zapping those....

User

Posted 07 Nov 2022 at 19:03

Bailey, was there a reason for not zapping the nodes at the same time. I often see references saying up to 5 areas can be treated.

Thanks Chris

User

Posted 07 Nov 2022 at 22:41

Chris that's a good question, I intend to look into. So the machine can be programmed to focus on several places at the same time?

I'll happily go in for 5 more radiotherapy sessions, but they may say, Oh well there's probably more about to appear, no point...?

User

Posted 08 Nov 2022 at 07:56

Originally Posted by: Online Community Member

Chris that's a good question, I intend to look into. So the machine can be programmed to focus on several places at the same time?

I'll happily go in for 5 more radiotherapy sessions, but they may say, Oh well there's probably more about to appear, no point...?

Bailey, I don't know the answer, I see guys on here who have had multiple areas treated with SABR ,but I can't see details of how the treatment was done.

I am sure our scholars will know.

Thanks Chris

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Radiotherapy on bone - how long for PSA to drop?

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