Tag: Ga68 PSMA PET Scan

Month 184 – PSMA Explained & Next Steps

On By DanIn Hormone Therapy, imaging, Prostate Cancer4 Comments

After last week’s PSMA PET scan, I did a little more digging into how the scans work, and why they don’t work for 10% to 20% of patients.

Prostate specific membrane antigen (PSMA) is a protein that’s found in healthy prostate cells, and it continues to exist in prostate cancer cells in most, but not all, cases.

PSMA in Imaging

Researchers found a way to attach a radioactive tracer to the PSMA proteins which would light up when seen in a PET scan, indicating the presence of cancer. Gallium-68 is the most commonly used tracer, with fluorine-18 also being used.

When the tracer is injected into the patient, it seeks out cells that have expressed the PSMA protein and attaches to them. The PET scanner then looks for areas where there is a build-up of the tracer to indicate where the cancer is located.

I’m going to use a grossly over-simplified analogy based on my reading as a lay person.

We all know that magnets are attracted to steel or iron. Imagine that the cancer cells with the PSMA protein are small steel ball bearings, and the radioactive tracer is a bunch of tiny magnets. Inject the magnets into your system, and they go in search of the steel ball bearings. When they find them, they attach, and the PET scan can see where all the magnets are located.

But for those patients whose cancer cells do not have the PSMA protein, that essentially means that the cancer cells are plastic balls, and the magnets that were injected will never attach to them. The PET scan won’t see any build-up of magnets/cancer cells.

Based on my experience with four PSMA PET scans, I believe that I’m in that 10% group and that my cancer cells do not express the PSMA protein—they’re the plastic balls.

PSMA in Treatment

In addition to using PSMA positive cells for imaging purposes, researchers have also recently developed a treatment that uses the PSMA positive cells. It goes by the brand name Pluvicto, but also known as Lutetium-177–PSMA-617.

It’s only used on patients with castration-resistant prostate cancer that have PSMA proteins.

The difference between using gallium-68 or fluorine-18 and lutetium-177 is that the lutetium is a radioactive material that attaches to the PSMA protein cells and delivers beta particle radiation to kill the cells.

This means that for those patients whose cancer doesn’t express the PSMA protein, this treatment option would not be available.

Alternative Imaging

On the good news front, there are other imaging options out there, one of which is Axumin (18F-fluciclovine). Instead of targeting PSMA in the cancer cells, it looks at the amino acids.

Axumin scans aren’t as sensitive as PSMA PET scans, but they are more sensitive than choline-11 scans.

At my current PSA level (2.52 ng/mL), the Axumin scan should have a decent chance of finding something.

In a conversation in a prostate cancer forum, I learned that one patient had used the gallium-68 tracer for his PSMA PET scans with the same results as mine, but they switched to PYLARIFY (piflufolastat F 18) as the tracer (which also attaches to the PSMA) and found four lesions using the different radiotracer. I know that one anecdotal case doesn’t mean much, but it’s something I can ask my team about.

Skip Imaging?

You may recall that, at one point, I had conflicting guidance from the urologist and oncologist on when to start androgen deprivation (hormone) therapy (ADT). One said when we saw metastasis, and the other said when my PSA hit 2.0 ng/mL. Clearly, I’ve passed the 2.0 threshold with my latest PSA results.

I went back and recalculated my PSA doubling time using only the last four values dating back to 10 March 2025. (The fourth and fifth values that I used before are 0.94 (January 2025) and 0.95 (March 2025), so having them so close may have skewed the results a little. When I used all five data points, my PSADT was 10.1 months; when I use the last four data points, it’s 8.9 months.

Given I’m past the PSA threshold (for one doctor) and the fact my PSADT is less than 10 months, I’m also wondering if there’s any value in continuing in the efforts to try and find the lesions. Or is is better, given how my PSA is increasing, to go ahead and just resign myself to the fact that I have micrometastases someplace and start the ADT sooner rather than later? In the time that it takes to schedule another scan, regardless of the type, my PSA could be well over 3.0 and even pushing 4.0.

That leads me to another question. If we do start the ADT and it knocks my PSA down to <0.1 like it did when I had it for salvage radiation therapy, does that mean that scans wouldn’t be able to locate the cancer while on ADT?

To my way of thinking, knowing where the cancer is at is important, even if it means letting the PSA run unabated for a short while longer. But what the hell do I know? I’m all ears for experiences from others that may have been in the same or similar situation.

Summary

Again, this is my lay person interpretation of things that I’ve researched, so please take this with a pound of salt. If you know I’m wrong on my interpretation, please let me know and provide references as to why I’m wrong. I want to learn.

You can rest assured, though, that this will be a part of my conversation with my team on 24 March.

Stay tuned for more.

Be well.

Header image: Desert wildflowers, Anza-Borrego Desert State Park, California

Day 5,593 ¾ – Scan Results

On By DanIn imaging, Prostate Cancer7 Comments

In the hour or so since my last post, my scan results were posted online:

“No evidence of recurrent prostate cancer or metastatic disease.”

<Sigh>

Needless to say, I have mixed emotions about these results.

I just want an explanation so that we can figure out next steps. After four scans with the same results, I’m of the mindset that I’m in the 10% of patients for whom PSMA PET scans don’t work.

You can bet I’ll be talking about other imaging options during my upcoming appointment, as well as any other plausible explanations for what’s going on.

At this point, I’m tired, frustrated, and stymied.

Day 5,593 ½ – Scan No. 4 Completed

On By DanIn imaging, Prostate CancerLeave a comment

My fourth PSMA PET scan is in the books. If I keep this up, I should join a PSMA PET scan loyalty club—have five scans and get the sixth one free.

It started with me drinking 500 ml of water two hours before the the scan. On arrival, I was weighed (I guess to help calculate how much Gallium-68 to inject?), and the tech started an IV. He walked away and wheeled in a cart with a small, lined box containing the injection syringe, and pushed the glow juice into my arm through the IV.

Once the juice was in, he removed the IV, and I leaned back in my recliner for the hour-long wait for the juice to make its way through my system. At the end of the hour, we headed to the scanner room where I emptied my pockets, jumped on the scanner table, and got strapped in so my arms wouldn’t move.

The scanner wasn’t claustrophobic for me, and it took 41 minutes to run up my body (they start at the thighs and work their way up to the head).

When I was through, I hopped off the table, collected my things, and headed home.

I have to admit that when I walked out of the hospital, I was really surprised by how much my body and mind unwound from the apparent subconscious nervous tension I was harboring. Going into it, I didn’t seem fazed by it all. It was routine for me. Heck, I’m on a first-name basis with the nuclear medicine tech (we’ll call him Sam) because he’s done all three of my scans at the VA. But apparently my subconscious had a different experience. Oh well. Nothing a good nap won’t cure.

I asked Sam how quickly the results would be available, and he said it could be as soon as this afternoon, but within 48 hours if they’re not.

From my previous scans with Sam, I’ve learned to not even think of asking him if he saw anything of concern during the course of the scan. He resoundingly (and rightly) always answered that it’s up to the doctor to interpret and provide the results.

I’ve also come to know that, for Sam, bedside manners seem to be optional. He’s not unprofessional in any way, but he is all business and sometimes even borders on the grumpy side. As I was leaving, Sam said something in such a way that he let his tough façade down. His voice became just a hint softer as he said, “You take care now” in a caring way.

Of course, that caught my attention and got my mind racing. I’m really, really, really trying not to read too much into that and get ahead of the actual results, but he said it two more times before I left. That makes me wonder what he saw that may have changed his demeanor.

Of course, my exhausted Gallium-68-infused brain may be making all this crap up, and I may get a good laugh out of it in a day or two. Or not.

As usual, stay tuned for the next chapter in this saga. I have my appointment to go over the results on 24 March.

Be well!

Header image: Anza-Borrego Desert, California

Month 182 – PSMA PET Scheduled

On By DanIn imaging, Prostate CancerLeave a comment

I held off on this post until I was able to get my PSMA PET scan scheduled this week.

I had been playing phone tag with the scheduler and, when I finally got to speak with him, I learned that they normally don’t schedule until 30 days in advance of the request date. Because the order for the scan said March, they weren’t going to call until next month. Fortunately, because we were already on the phone, the scheduler went ahead and put me on the calendar for 4 March 2026.

That should give enough time to interpret the results before my 24 March appointment with the urologist. I’ll go for a PSA test just before the scan on 2 March.

I continue with my pelvic floor physical therapy every other week. I’m not sure that it’s been having an effect on my incontinence, so I’ll have to ask how long it takes before I have any truly noticeable improvement.

Other than that, there’s not much else to report. Just another day living with prostate cancer.

Be well.

Header image: Anza-Borrego Desert, California

Day 5,522 – Urologist Appointment

On By DanIn Hormone Therapy, imaging, Prostate Cancer, Treatment9 Comments

Late last week, I received a text message asking if I would like to move my urologist appointment from 30 December to today, 23 December, and I agreed.

My appointment was at 3:15 p.m., and I arrived around 2:45 p.m. As I’m walking up to the check-in kiosk, my cell phone rings, and it was the urology department wanting to confirm that I’d be there. That’s the first time that that’s happened, and I told the nurse that I was checking in as we spoke. “Great! We’ll come out and get you.” Apparently, they were antsy to get out of there early on the day before Christmas Eve. So was I.

The head of the department was the one who saw me this time, and we had a really good conversation. Some of the key takeaways:

  • She was concerned about the increase in my PSA but not panicked, even initially suggesting we just continue to monitor it.
  • We talked at length about doing another round of imaging to see if we can determine the location of the cancer.
  • We agreed to do another PSMA PET scan, and we negotiated doing one in March 2026. (She thought that Nuclear Medicine might push back on doing one sooner, i.e., within a year, as the last one I had was in March 2025.) She also mentioned the possibilities of other imaging should the PSMA PET scan come up with no evidence of cancer/metastasis for the fourth time.
  • We talked about the timing of starting androgen deprivation (hormone) therapy. She wouldn’t start it until there was evidence of metastasis, but was open to starting it earlier if I really wanted to do so.
  • Lastly, we reviewed my stress incontinence and nocturia issues and talked about my pelvic floor physical therapy.

It was one of the more thorough discussions that I’ve had at the VA, and I’m okay with the plan coming out of the meeting. I’ll go for another PSA test on 1 March; hopefully get the PSMA PET scan scheduled in early March; and have a follow-up with the urologist on 24 March.

I’m glad I got this out of the way before the holiday. I’ve got my answers, plus it frees up next week for me to go out an play if I want.

Merry Christmas, Happy New Year, and be well!

Header image: Hotel del Coronado at Christmas, Coronado, California

Month 179 – Urologist Discussion

On By DanIn Hormone Therapy, imaging, Prostate Cancer, Radiation Therapy1 Comment

Well, that went about as I expected.

In a nutshell, we’re punting the ball another three months down the road.

The doctor commented on the continuing rise in my PSA and said after consulting with the doctor who saw me last time, said that he wanted to recheck my PSA in six months and “wait a year” for another PSMA PET scan. I should have asked for clarification on that, but I think he was referring to waiting a year after my last PSMA PET scan in March 2025 and not a year from today.

I wasn’t entirely comfortable with waiting another six months, so we agreed to test PSA again in December (three months after my September test) and go from there.

We also talked about spot radiation if anything pops up on the scan. He seemed a bit reluctant for that to be an option, and went straight to starting hormone therapy. It’s as though he was making the transition from curative options to management options, and, to be perfectly honest, I believe I made that transition in my own mind once the salvage radiation failed. That doesn’t mean that I wouldn’t try zapping a lesion or two if they popped up on the scan depending on location (no more zapping to the pelvis and risking further bowel complications).

We did talk about my experience with hormone therapy during the salvage radiation, and the timing of starting it this time around. In that discussion, he brought up the topic of bringing in a medical oncologist at some point depending on the scan results and my PSA test results.

We talked at length about my urinary frequency and some options for that. He suggested some pelvic floor therapy might be beneficial, so I said I’d be willing to give that a try.

Overall, I’m okay with where we’re at and the planned course of action for now. I’ll go for my PSA test in early December, and if there’s another significant jump, I’ll press for the PSMA PET scan to be done sooner rather than later.

My next scheduled urologist appointment is 30 December 2025.

Be well!

Header image: Sunset, Imperial Beach, California

Day 5,256 – Doctor Visit

On By DanIn imaging, Prostate Cancer7 Comments

I had my post-PSMA PET scan visit with the urologist today, and I wasn’t really sure what to expect going into it.

The doctor (same as last time) shared the scan results saying that they’re something I should celebrate. I mentioned, though, that I have had three scans and were inconclusive despite the rising PSA numbers. He was quick to reply by saying that the scan not showing evidence of prostate cancer or metastasis was conclusive.

I understand where he’s coming from, but until we know where the cancer is, I’m going to have a difficult time accepting that perspective.

I did ask whether there was some sort of test that can determine if my cancer doesn’t express PSMA, and he said that there wasn’t. Something in my pea-sized brain tells me I need to double check him on that.

I also asked if there could be another explanation beyond the cancer that would explain my rising PSA. He ruled out the possibility of some residual prostate tissue being left behind after the surgery as being the cause based on my PSA kinetics over time.

In terms of what’s next, we’re kicking the can six months down the road for another PSA test and follow-up. I was a bit surprised that he wanted to wait six months, and suggested doing the test in three or four months. He was a bit insistent on the six month window. He felt comfortable with my current situation—the slight increase in my last PSA test from the previous one and my PSA doubling time—that waiting six months wouldn’t be a problem. He also argued that having a longer period between tests would better reflect what’s going on.

As we wrapped up, he reminded me that the scan results were good news, and I know that he’s right in that regard. I’ll work on changing my own perspective going forward (even though those little cancer bugs are still doing their thing inside me.)

My follow-up appointment is on 30 September 2025.

That’s it for today. Be well!

Header image: Cherry Blossoms, Japanese Friendship Garden, San Diego, California

Gallium supply to the U.S. cut off by China

On By DanIn imaging, Prostate Cancer2 Comments

This headline on the AP News feed caught my attention this morning:

China bans exports to US of gallium, germanium, antimony in response to chip sanctions

When you read the article, it omits any reference to gallium being used in medical diagnostics, so I have to wonder if this ban will adversely impact the ability to do 68Ga PSMA PET scans.

That question led me to a quick Google search on the production of 68Ga that yielded:

I’m no nuclear physicist or radiopharmaceutical guy but, given that process outlined above, it sounds to this layperson that PSMA PET scans could possibly be impacted.

Or I could be completely out to lunch, reading far too much into the story.

It’s definitely something to keep and eye on going forward, as I’m guessing another PSMA PET scan is in my future in January or February.

Day 5,118 – Urologist Visit

On By DanIn Hormone Therapy, Prostate Cancer, Radiation Proctitis9 Comments

I met with the urologist this afternoon to go over my most recent PSA test results and the plan going forward. In a nutshell, we agreed to remain in limbo for another three months and retest the PSA in January and consider a PSMA PET scan if warranted at that point. (She was a bit skeptical that the PSMA PET scan would be conclusive even at my current PSA of 0.69 ng/mL.)

The urologist thought it was a little premature to start talking about androgen deprivation therapy, but recognized that that’s the next likely step down this path. I mentioned that, when I met with the urologist and medical oncologist in February, one suggested ADT at metastases and the other suggested starting at a PSA of 2.0 ng/mL. She said she could understand both positions.

Bottom line is that I continue to be in this sort of “no man’s land” of prostate cancer. We know it’s there; we just don’t know where, and we don’t want to pull the trigger on ADT prematurely. So more waiting.

One other thing that we discussed was radiation proctitis.

Graphic Biology Ahead

I’ve been sitting on this little tidbit for a while now, but I’ve been noticing blood in my stools. It initially appeared as spots a little smaller than a dime coin (~ 1 cm) but, over time, it has subsided to a small streak or a hint of blood. You know me: I had to create a spreadsheet to track it, and it’s been occurring in about ten percent of my bowel movements. That makes me feel better that it isn’t happening each and every time—that might indicate a larger problem if it were happening every time.

Fortunately, I haven’t had the diarrhea or mucus discharge that can come with more severe cases of radiation proctitis.

I mentioned this to my primary care physician during my appointment on 4 November, too. Both he and the urologist recommended a colonoscopy to check out what’s really going on. That joyful experience is scheduled for Friday, 22 November. Yippee!

I did come across this continuing education paper that gives a good overview if you’re really interested in learning more:

Radiation Proctitis

So the journey continues. Stay tuned for the next installment.

Header image: San Diego skyline and Mission Bay from Kate Sessions Memorial Park

Day 4,830 – PSMA PET Scan

On By DanIn imaging, Prostate CancerLeave a comment

PSMA PET scan No. 2 is behind me.

This was different from and easier than the first one. That’s because the VA just did a PET scan today, whereas my scan at UCLA included a CT scan on top of the PET scan.

That fact really didn’t occur to me until all was said and done. I’ll have to ask the doctor about the đifferent approaches.

In any case, today they juiced me up with Gallium-68 shortly after arrival. About 45 minutes later, I was on the scanner table ready to go. I barely felt the table move me through the scanner, and it took about 45 minutes to complete the scan.

Of course, the technician wouldn’t give me any sneak peak insights. “The doctor will interpret the scan.” I expect it could take a week or so for me to see any notes in my online records.

Again, even with my PSA closing in on 0.40 ng/mL, there’s only about a 50-50 chance it will give us any useful information at that PSA level. (As a refresher, my PSA going into the UCLA scan was 0.22 ng/mL.)

More to come.