18F-sodium fluoride PET-CT appeared to be a more accurate identifier of bone metastases in patients with prostate cancer.

[Scout4answers]

This seem like old news

18F-Sodium Fluoride PET-CT Detects Bone Metastases More Accurately in 2 Cancers

December 29, 2022

Nicholas Wrigley

18F-sodium fluoride PET-CT appeared to be a more accurate identifier of bone metastases in patients with breast and prostate cancer than the standard SPECT method.

Bone metastases were more accurately detected with the use of 18F-sodium fluoride (18F-NaF) PET-CT imaging in patients with high-risk breast and prostate cancer than 99mTc-methylene diphosphonate (99mTc-MDP) single-photon emission CT (SPECT) imaging, according to findings from the phase 3 MITNEC-A1 trial (NCT01930812).

18F-NaF PET-CT imaging detected osseous metastases with an accuracy of 84.3% (95% CI, 79.9%-88.7%) compared with 77.4%(95% CI, 72.3%-82.5%) for 99mTc-MDP SPECT imaging, translating to an overall difference of 6.9% (95% CI, 1.3-12.5; P = .016). 18F-NaF PET-CT also demonstrated higher sensitivity and negative predictive value vs 99mTc-MDP with no significant difference in specificity or positive predictive value. Moreover, no dose reductions were necessary in either group, as there were no reports of adverse effects (AEs) of grade 1 or higher.

“Accurate detection of osseous metastases is important for staging, treatment planning, monitoring response to therapy, and detection of areas at risk for skeletal-related adverse events in patients with a wide range of malignancies,” the investigators wrote. “99mTc-MDP SPECT has been considered as the method of choice for the evaluation of bone metastases in various cancers. Since the limited spatial resolution of planar scintigraphy and SPECT affects the sensitivity of bone scintigraphy for the detection of bone metastases, transition to the higher resolution of PET-CT with the use of 18F-NaF for the detection of these metastases is appealing.”

Investigators enrolled 288 patients from July 11, 2014, to March 3, 2017. An evaluable imaging core population that included 204 patients with prostate cancer and 57 with breast cancer was extracted from this enrolled cohort. Median ages were 68.8 (95% CI, 63.0-74.4) and 58.5 years (95% CI, 49.7-66.8) in the prostate and breast cancer groups, respectively. All patients in the prostate cancer group were men and 96% of those in the breast cancer group were women. The vast majority of patients in both groups were White (79% vs 81%, respectively).

In the overall group, 42% (n = 109) of patients experienced bone metastases, including 44% (n = 90) of those with prostate cancer and 33% (n = 19) of those with breast cancer. The median follow-up was 735 days (interquartile range [IQR], 727-750).

According to a post-hoc subset analysis, 18F-sodium fluoride PET-CT performed better than the 99mTc-MDP SPECT in terms of accuracy, sensitivity, and negative predictive value in the prostate cancer group, but both methods had equivalent specificity and positive predictive value. Meanwhile, in the breast cancer group, 18F-sodium fluoride PET-CT demonstrated better accuracy, specificity, and positive predictive value, but had the same sensitivity and negative predictive value as its counterpart.

18F-NaF PET-CT also detected significantly more metastatic bone lesions than 99mTc-MDP SPECT in the 65 patients whose metastases were detected on both scans (P <.0001).

In terms of physiological effects, 18F-NaF PET-CT led to vital sign fluctuation between the pre-injection timepoint and 60 minutes after the 18F-NaF injection, but the changes were not deemed clinically significant.

“Considering all the advantages and the ability to detect bone metastasis with higher sensitivity and accuracy, 18F-NaF has the potential to displace 99mTc-MDP as the bone imaging radiopharmaceutical of choice,” the investigators concluded.

Reference

Bénard F, Harsini S, Wilson D, et al. Intra-individual comparison of 18F-sodium fluoride PET-CT and 99mTc bone scintigraphy with SPECT in patients with prostate cancer or breast cancer at high risk for skeletal metastases (MITNEC-A1): a multicentre, phase 3 trial. Lancet Oncol. 2022;23(12):1499-1507. doi:10.1016/S1470-2045(22)00642-8

[cesces]

I'm not familiar with "99mTc-MDP SPECT" scans.

Does anyone know how 18F-sodium fluoride PET-CT compares with PSMA scans?

[6357axbz in reply to cesces]

good question

[cesces in reply to 6357axbz]

I have lots of good questions.

Not so many good answers.

There are others here though that often have surprisingly good answers.

Hopefully we will hear from one of them.

[Flash64 in reply to cesces]

I've had both. 18F is definitely more sensitive than PSMA-PET and MRIs to bone changes. There doesn't need to be any active cancer in the bones for these changes to show up. My PSA is undetectable and it showed several areas of bone that were not identified in earlier MRIs or a PSMA-PET (PSA of 50 for MRI and 0.19 for PSMA-PET). Close comparison to previous MRIs and the PSMA-PET scan indicated that these were existing sites that were missed by the radiologist in those scans as they were quite small. Hope this helps.

[cesces in reply to Flash64]

Hmmm so very interesting.

So why isn't 18f used more and psma used less?

Or at least why all the noise about psma, and all the silence about 18f?

[leebeth in reply to cesces]

Flash64’s PSA was undetectable so it is not surprising that a PSMA would not find anything. The vast majority of men being scanned with a PSMA scan have much higher PSAs, in which case PSMA has been proven to be more sensitive.

[Flash64 in reply to leebeth]

Hi leebeth. My PSA wasn't undetectable at the time of the PSMA-PET scan, though it was low at about 0.19. There was still uptake in my prostate, despite completing Docetaxel, a year of Lupron and 8 months of Zytiga.

[leebeth in reply to Flash64]

Since the tracer is secreted through your urine, there is usually uptake in your prostate. That doesn’t mean there is active cancer there.

PSMA scans with a PSA that low would be expected not to detect much if anything.

[Flash64 in reply to cesces]

I think the imaging space is continuing to evolve so I'm not too surprised. 18F is probably the best for looking at bone mets, but PSMA-PET will show both soft tissue and bone mets, providing they are producing the necessary antigen.

[Tony666]

I had both - a psma pet scan and a NaFL pet scan at NIH. The psma pet scan showed some avidity on a rib. They did a follow up NaFl pet scan which did not. They concluded that the psma pet scan had shown a false positive and was slightly avid due to some other reason than cancer. Just anecdotal but in my case, the NIH doctors seemed to feel the NaFL pet scan trumped the psma pet scan.

[RMontana]

This prompts the question; PSMA PET vs 99mTc-MDP SPECT. There is a stufy (looks like in Egypt) on this matter...dont know if its complete. Here is the LINK. If anyone knows the answer to the question let me know. TNX

"The aim of this study is to compare the pooled sensitivity, specificity, and accuracy of 99mTc-PSMA SPECT/CT and 68Ga-PSMA PET/CT in patients with prostate cancer."

ejrnm.springeropen.com/arti...

[RMontana]

Here is the comparison between PSMA PET and 18F-NaF PET/CT. Looks like we have a clear advantage with both scans for bone met.

Conclusion: In comparison to 68Ga-PSMA-11 PET/CT, 18F-NaF PET/CT detects a higher number of pathologic bone lesions in advanced stage PC patients scheduled for radionuclide therapy. Our data suggest that 68Ga-PSMA-11 PET should be combined with 18F-NaF PET in PC patients with skeletal metastases for restaging prior to initiation or modification of therapy.

pubmed.ncbi.nlm.nih.gov/297...

[cesces in reply to RMontana]

The accuracy of 68Ga-PSMA-11 PET/CT is substantially affected by the level of PSA, at least up to 2.0 PSA.

Does anyone know if the accuracy of 18F-NaF PET/CT affected by the level of PSA?

And how the accuracy of the two tests compare at PSA levels of 2.0 or greater?

[RMontana in reply to cesces]

That is a good question. I got a PSMA PET at UCLA Med Center in January, 2020; was one of the first in FL to get this scan. I was on Lupron and my PSA was 0.01 or lower. I talked to Dr Calaise at UCLA about this. I asked him if I had significant tumor growth but low PSA would the scan pick up the tumor? He said it would. I then got my scan, found nothing in terms of MET and proceeded with my IMRT to the Prostate fosa and pelvic lymph nodes.

I did some more reading and it appears that the persisten sensitivity of the PSMA PET at low PSA is correlated to the surface protein of the PCa tumor, not the level of PSA. So if you had a large tumor but it was dormant because of ADT treatment it would not put out PSA but could not hide due to its surface protein profile (its exterior structure). This is what I understood from Dr Calaise...so if you had a significant tumor that was asleep due to ADT its surface area, or protein structure, would still be avaiable for the PSMA PET binding and therefore for discvovery. It explains here why a fellow brother here had PSA of 0.03 yet PSMA PET found bone tumors; they were up to 7mm in size! I believe the PSA limit of 0.02 is also misleading if you are on ADT! Of course your PSA would be low, but if you had significant tumor growth its PSMA protein would still be exposed to discovery.

If anyone knows otherwise please expound.

[cesces in reply to RMontana]

My understanding was that it is best to get off ADT and let the PSA rise before getting a scan

[6357axbz in reply to cesces]

that what I did before my first PET-PSMA G68 scan at UCLA. My MO advised me to wait till my PSA rose to between 0.5 and 1.0

[cesanon in reply to 6357axbz]

If you look at Tall_Allen's data on his website, PSA 2.0 is the safest level to wait for.

That is if you want to avoid false negatives.

I am of the school that I want to just take one scan, and make sure it is as accurate as can be.

"One and Done" LOL

[6357axbz in reply to cesanon]

That data, if I’m reading the reading the arrival you’re referring to, is from 2016. Not sure how valid that is today…

[cesanon in reply to 6357axbz]

Yes. A lot can happen in 7 years.

I got the impression that the performance of these scans was improving at low PSA levels. Certainly the Docs seem to be using them at lower PSA levels.

It would be nice to see more current numbers.

Tall Allen is pretty good at keeping his pages updated. It would seem if things were changing he would make some mention of that.

[6357axbz in reply to cesanon]

agreed

My MO was adement that I get a pllarify scan even though my PSA wa still undetectable so she had a “baseline”. I don’t completely understand this but will discuss next face to face

[dhccpa]

How about Axumin PET? I've had three of them but never had a PSMA scan. Axumin was new until it wasn't, but must still rank up there.

[cesanon in reply to dhccpa]

It seemed when it first came out everyone was treating Axumin PET as the poor cousin of the PSMA scans.

But I don't know on what basis or data this was being done.

[dhccpa in reply to cesanon]

thanks. That was kind of my impression as well.