MRI for prostate planning?

[metview]

How often do you all get an MRI specifically for prostate contouring for conventional/hypofractionated radiation (20-40 fx)? I don't have an MRI sim and it can take up to 4-6 weeks to get diagnostic MRI scheduled. I've found that it only helps with delineating the inferior aspect, and even then, it only helps by contouring the last 1 slice (3 mm). Curious as to what others are doing?

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[TheWallnerus]

I do it in all cases. I use the fiducials to fuse MRI (and a slightly unique MR sequence) to CT, high-accuracy-like. I would imagine unless you live in a really rural area you could shop around to some outpatient imaging centers, offer them business, and have them do the MRIs a lot quicker than a 6 week delay.

 

[NotMattSpraker]

I do it in all cases. I use the fiducials to fuse MRI (and a slightly unique MR sequence) to CT, high-accuracy-like. I would imagine unless you live in a really rural area you could shop around to some outpatient imaging centers, offer them business, and have them do the MRIs a lot quicker than a 6 week delay.

Its funny how if you just say "Thats a pretty long wait, I guess Ill have to look for other imaging centers", the schedule opens up!

I also get an MRI for every patient. I had one recently that could not and I did a urethrogram. Im cool to never do that and I think my team will be too.

Im not sure the best data that argues sparing inferiorly helps erectile function, but thats the theory Im working off.

Im trying to move my system to pre-biopsy MRI, thats really the way we should all move. MR for RT planning is always available then.

 

[MidwestRadOnc]

Always. Start referring out imaging then have a convo with admin.

 

[MidwestRadOnc]

I do it in all cases. I use the fiducials to fuse MRI (and a slightly unique MR sequence) to CT, high-accuracy-like. I would imagine unless you live in a really rural area you could shop around to some outpatient imaging centers, offer them business, and have them do the MRIs a lot quicker than a 6 week delay.

What Mr sequence do you use for fiducual fusion?

 

[Palex80]

I do it in all cases. I use the fiducials to fuse MRI (and a slightly unique MR sequence) to CT, high-accuracy-like.

Wow, that's smart! Do you have any special type of fiducials to recommend? I am concerned about having difficulties delineating the intraprostatic boost volume (for FLAME/DELINEATE-like boosts) if the fiducials are placed before the planning MRI. Will I have issues with MRI artefacts or bleeding/trauma due to the fiducials, that may make my boost-contouring less accurate?

Im trying to move my system to pre-biopsy MRI, thats really the way we should all move. MR for RT planning is always available then.

Yes, all patients should have an MRI prior to a biopsy.

 

[Gfunk6]

I only get MRIs for prostate SBRT. I use a high-res T2 sequence through the prostate to help with urethral deliniation.

 

[seper]

Routine MR for traditional prostate RT is wasteful, IMO

 

[MidwestRadOnc]

Routine MR for traditional prostate RT is wasteful, IMO

It’s not very uncommon I have a guy with GG2 PSA 12 and find SVI on an MRI. That changes treatment. Also I always focal boost if possible.

 

[TheWallnerus]

Do you have any special type of fiducials to recommend? I am concerned about having difficulties delineating the intraprostatic boost volume (for FLAME/DELINEATE-like boosts) if the fiducials are placed before the planning MRI. Will I have issues with MRI artefacts or bleeding/trauma due to the fiducials, that may make my boost-contouring less accurate?

There are MR-compatible (carbon based) fiducials out there now that are small. But I have always used 1x3mm gold seed markers, and I can get them to show up on T2 turbo spin sequences (I get a rads nerd to help me set the particulars) just fine. They do not distort the MR images. There is almost no artifact. Wait at least a week after marker placement for the MRI and there will be no bleeding issues. I googled DELINEATE and it looks like they put in (3... I have always used 4...) gold markers prior to MRI?

In Eclipse (and I'm sure other TPSs), you can put in matching points and do image fusion that way (versus image-based). The seeds become the match points. This method gives me high confidence in MR/CT match w/ fiducials and would show near-zero inter-user MR/CT match variability.

The argument for MR-fusion for all prostates is that I feel it makes some change to my prostate contouring in at least about 1 in 3 cases. Amar Kishan showed us (I already knew it, natch!) that even a couple mm of contouring difference can affect changes in toxicity outcomes.

 

[BobbyHeenan]

There are MR-compatible (carbon based) fiducials out there now that are small. But I have always used 1x3mm gold seed markers, and I can get them to show up on T2 turbo spin sequences (I get a rads nerd to help me set the particulars) just fine. They do not distort the MR images. There is almost no artifact. Wait at least a week after marker placement for the MRI and there will be no bleeding issues. I googled DELINEATE and it looks like they put in (3... I have always used 4...) gold markers prior to MRI?

In Eclipse (and I'm sure other TPSs), you can put in matching points and do image fusion that way (versus image-based). The seeds become the match points. This method gives me high confidence in MR/CT match w/ fiducials and would show near-zero inter-user MR/CT match variability.

The argument for MR-fusion for all prostates is that I feel it makes some change to my prostate contouring in at least about 1 in 3 cases. Amar Kishan showed us (I already knew it, natch!) that even a couple mm of contouring difference can affect changes in toxicity outcomes.

Same here in my practice , though I must admit sometimes the fiducials do not show up as well as I’d like on our T2 sequences. Been working with physics and phantoms to see if we can get better.

 

[TheWallnerus]

Same here in my practice , though I must admit sometimes the fiducials do not show up as well as I’d like on our T2 sequences. Been working with physics and phantoms to see if we can get better.

Some potentially helpful info in here:

Comparison of MRI sequences in ideal fiducial maker-based radiotherapy for prostate cancer

Prostate contouring using CT alone is difficult. To overcome the uncertainty, CT/MRI registration using a fiducial marker is generally performed. However, visualization of the marker itself can be difficult with MRI. This study aimed to determine the ...

www.ncbi.nlm.nih.gov

 

[SneakyBooger]

MRI for all who have no contraindication in my practice.

Just reading over the DELINEATE protocol this morning and it states:
"Evidence suggests that the prostate gland is visualized better and defined more accurately on MRI than on CT."

No citation given in the body of text. Maybe it's in a reference at the end of the protocol.

 

[RadRadRad]

MRI for all who have no contraindication in my practice.

Just reading over the DELINEATE protocol this morning and it states:
"Evidence suggests that the prostate gland is visualized better and defined more accurately on MRI than on CT."

No citation given in the body of text. Maybe it's in a reference at the end of the protocol.

There is definitely data on this from 10+ years ago.
I think with lots of practice one can get pretty good on CT alone but certainly easier with mri

 

[TheWallnerus]

There is definitely data on this from 10+ years ago.
I think with lots of practice one can get pretty good on CT alone but certainly easier with mri

Great point I was gonna make. If you use MR/CT to contour for about a year, and suddenly had to go back to just CT, you would find you were now drawing smaller prostates than before you became exposed to CT/MR contouring.

 

[Chartreuse Wombat]

There is definitely data on this from 10+ years ago.
I think with lots of practice one can get pretty good on CT alone but certainly easier with mri

Initial clinical assessment of CT-MRI image fusion software in localization of the prostate for 3D conformal radiation therapy - PubMed

CT-MRI image fusion study made it possible to compare the two modalities directly. MRI localization of the prostate is more accurate than CT, and indicates the distance from cone to apex is 15 mm. CT-MRI image fusion technique provides valuable supplements to CT technology for more precise...

pubmed.ncbi.nlm.nih.gov

 

[grenz]

I’m of two minds in this. 1, it’s nice to feel very confident of the apex delineation. On the other, with todays high deductible plans, this means the patients are getting hit with a $1000+ bill so I can subtract an extra slice inferiorly.

 

[ramsesthenice]

It’s a continuum. Unquestionably, you can delineate the prostate and low rectum (at the pelvic floor) better on MRI. Volumes will usually be a bit smaller if you contour on MRI. Of course, one could argue (as some do), if MRI is better for sim, it’s better for IGRT. It comes down to deciding how much better “better” is.

I personally don’t do MR sims for my non MRL patients most of the time.I’ve done so much contouring on MRI (for MRL cases) and the concordance is usually very good after years of practice. If I can’t see things well, I will fuse their diagnostic MRIs which 99.9% of my patients come with. It’s standard staging and I agree with the above comments that everyone should have an MRI as part of their work up these days. Even if you don’t do FLAME boosting, it’s good to know where the gross disease is. If it’s in the apex, then defining it is pretty important etc.

 

[metview]

The patient in question was de novo high volume metastatic prostate cancer 5 yrs ago (had PSMA and axumin, but never had MRI prostate) who has prostate only progression, so this MRI would only be for planning purposes. Would that change anyone's answer?

 

[TheWallnerus]

The patient in question was de novo high volume metastatic prostate cancer 5 yrs ago (had PSMA and axumin, but never had MRI prostate) who has prostate only progression, so this MRI would only be for planning purposes. Would that change anyone's answer?

Well I just wanna know how you’re getting a payor to pay for prostate only RT in someone originally diagnosed with high volume M1 disease. Or what the data is for prostate only RT in that case

 

[Ray D. Ayshun]

Well I just wanna know how you’re getting a payor to pay for prostate only RT in someone originally diagnosed with high volume M1 disease. Or what the data is for prostate only RT in that case

Sounds like he's describing oligoprogression.

 

[Mandelin Rain]

He's probably symptomatic. A little frequency or urgency? Call it palliative.

 

[evilbooyaa]

The patient in question was de novo high volume metastatic prostate cancer 5 yrs ago (had PSMA and axumin, but never had MRI prostate) who has prostate only progression, so this MRI would only be for planning purposes. Would that change anyone's answer?

Are you doing 55/20 or lower EQD2? If so, I would just treat based on CT.

But , for localized prostate cancer, dedicated multiparametric MRI of the prostate should be SOC either before OR after biopsy.

Lots of places will do them, including imaging centers outside your institutional network.