Liver SBRT and being rural

[Ray D. Ayshun]

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I'm more in this camp. I take a look at the how tumor is moving (more pertinent for lung I suppose) and the lateral motion is usually not as bad as the sup / inf. For VMAT based plans, there is more spread lateral along the axis of the plane. The dose fall off is much sharper sup / inf thus I sometimes enlarge my PTV in that direction due to the uncertainty of it all.

TBH with all that said I probably >90% of the time just do a concentric PTV.

I guess I do too as long as my ITV looks like humpty dumpty, Technically, that should account for motion. If it appears like there's some discord, I'll go to the sup/inf differential.

 

[scarbrtj]

Amen. I feel like a lot of people have it their heads that PTVs should be isotropic expansions based on setup and motion uncertainty. Using an isotropic expansion assumes uncertainty is even distributed in all directions but if your 4D tells you that motion is not evenly distributed in 3 dimensions that is not a great assumption. Some of my colleagues argue that when expanding from an ITV the additional uncertainty (beyond what is accounted for on 4D) should be relatively evenly distributed but I am not sure that is an entirely fair assumption. We are really splitting hairs here and in all reality this is mostly an academic debate.

can't resist an academic debate... Motion uncertainties (should) fall into the area of ITV creation. Ideally the ITV "covers" the true fact that (target or OAR) motion is never evenly distributed in 3 dimensions, or even 1D. ITVs can be "liberally" or "conservatively" created. E.g., one might choose gating and say the 40-60% phase is where I'm going to treat (smaller ITV)... or use gating to create a free breathing 0-100% phase ITV (bigger ITV)... or, like me, take multiple slow CTs and fuse them and create an ITV based on wherever the target is across multiple scans in time and space (even bigger ITV). HOWEVER... once an ITV has been created, one then is an area of where 1D uncertainties have appeared to be evenly distributed. And because 1D uncertainties are evenly distributed, 3D uncertainties are not evenly distributed as @wanderingstar once smartly pointed out. That 1D uncertainties have consistently appeared normally distributed allows for mathematical exercises where PTV "margin recipe equations" can be made. Or, in a more empiric approach that I favor (and no one does), just measure the non-normal distributed "drift shift" scalar (sometimes inappropriately called "vector") across many, many patients and make a PTV expansion which covers >95% of the scalars (ie covers >95% of the 3 DoF chi square distributions of the scalars)... this expansion does have to be isotropic when calculated this simply (easily).

 

[ramsesthenice]

can't resist an academic debate... Motion uncertainties (should) fall into the area of ITV creation. Ideally the ITV "covers" the true fact that (target or OAR) motion is never evenly distributed in 3 dimensions, or even 1D. ITVs can be "liberally" or "conservatively" created. E.g., one might choose gating and say the 40-60% phase is where I'm going to treat (smaller ITV)... or use gating to create a free breathing 0-100% phase ITV (bigger ITV)... or, like me, take multiple slow CTs and fuse them and create an ITV based on wherever the target is across multiple scans in time and space (even bigger ITV). HOWEVER... once an ITV has been created, one then is an area of where 1D uncertainties have appeared to be evenly distributed. And because 1D uncertainties are evenly distributed, 3D uncertainties are not evenly distributed as @wanderingstar once smartly pointed out. That 1D uncertainties have consistently appeared normally distributed allows for mathematical exercises where PTV "margin recipe equations" can be made. Or, in a more empiric approach that I favor (and no one does), just measure the non-normal distributed "drift shift" scalar (sometimes inappropriately called "vector") across many, many patients and make a PTV expansion which covers >95% of the scalars (ie covers >95% of the 3 DoF chi square distributions of the scalars)... this expansion does have to be isotropic when calculated this simply (easily).

What have I done getting this started???

In all seriousness, HCCs are not really that hard to treat. You just have to understand the technical limitations of the approach you are using and adapt accordingly. We (as a field) already made breast cancer WAY harder than it needs to be. Lets not do the same to HCC

 

[RadOncMegatron]

What have I done getting this started???

In all seriousness, HCCs are not really that hard to treat. You just have to understand the technical limitations of the approach you are using and adapt accordingly. We (as a field) already made breast cancer WAY harder than it needs to be. Lets not do the same to HCC

What? You have a problem with a proton breast trial?

ClinicalTrials.gov

clinicaltrials.gov

 

[ramsesthenice]

What? You have a problem with a proton breast trial?

ClinicalTrials.gov

clinicaltrials.gov

 

[evilbooyaa]

What have I done getting this started???

In all seriousness, HCCs are not really that hard to treat. You just have to understand the technical limitations of the approach you are using and adapt accordingly. We (as a field) already made breast cancer WAY harder than it needs to be. Lets not do the same to HCC

HCCs aren't that hard to treat when you know what you're doing. Whether one knows what they're doing or not for this technique is no guarantee across all US Rad Oncs. I would not trust every single Rad Oncs who finished training more than say 10-15 years ago with this technique. Most would probably be able to handle it just fine but I'm sure some subset who never does SBRT, or only does an occasional lung here or there, may not respect the differences in IGRT between lung or bone SBRT vs liver SBRT.

 

[Krukenberg]

HCCs aren't that hard to treat when you know what you're doing. Whether one knows what they're doing or not for this technique is no guarantee across all US Rad Oncs. I would not trust every single Rad Oncs who finished training more than say 10-15 years ago with this technique. Most would probably be able to handle it just fine but I'm sure some subset who never does SBRT, or only does an occasional lung here or there, may not respect the differences in IGRT between lung or bone SBRT vs liver SBRT.

Have talked to an academic attending at a different institution who was doing some locums, and the doc he was covering was treating liver SBRT without any motion management. Free breathing CT

 

[FrostyHammer]

Have talked to an academic attending at a different institution who was doing some locums, and the doc he was covering was treating liver SBRT without any motion management. Free breathing CT

"Ignorance is bliss"

 

[thecarbonionangle]

"Ignorance is bliss"

“My patients do excellent”, never sees them back. Sounds like classic old timer in our field.

 

[Mandelin Rain]

What dose constraints does everyone use for the central hepatic structures?

Who does the PV + 1.0/1.5?
BD?
Etc...

 

[Palex80]

I guess I do too as long as my ITV looks like humpty dumpty, Technically, that should account for motion. If it appears like there's some discord, I'll go to the sup/inf differential.

Back in the old days prior to 4D-CT, I was trained to do the following:

1. Perform the planning CT scan, keep the patient on the CT couch.
2. Identify the tumor on the CT scan.
3. Go to a CT slice 2 cm above the superior margin of the tumor contour.
4. Ask the patient to breath freely, then run 8 CT slices each 2 seconds apart on exactly that spot.
5. If no tumor visible on those CT slices --> all good. If margins needed to be tight, we would repeat the same procedure at 1cm above the tumor.
If tumor was visible at 2cm, then we would repeat the process at 3 cm superior to the tumor.
6. Do the same at the inferior margin of the tumor, using CT slices below the inferior margin.

🙂

 

[elementaryschooleconomics]

Back in the old days prior to 4D-CT, I was trained to do the following:

1. Perform the planning CT scan, keep the patient on the CT couch.
2. Identify the tumor on the CT scan.
3. Go to a CT slice 2 cm above the superior margin of the tumor contour.
4. Ask the patient to breath freely, then run 8 CT slices each 2 seconds apart on exactly that spot.
5. If no tumor visible on those CT slices --> all good. If margins needed to be tight, we would repeat the same procedure at 1cm above the tumor.
If tumor was visible at 2cm, then we would repeat the process at 3 cm superior to the tumor.
6. Do the same at the inferior margin of the tumor, using CT slices below the inferior margin.

🙂

What's this "prior to 4D-CT" time you speak of...is that something fancy in Europe? 😀

 

[evilbooyaa]

Back in the old days prior to 4D-CT, I was trained to do the following:

1. Perform the planning CT scan, keep the patient on the CT couch.
2. Identify the tumor on the CT scan.
3. Go to a CT slice 2 cm above the superior margin of the tumor contour.
4. Ask the patient to breath freely, then run 8 CT slices each 2 seconds apart on exactly that spot.
5. If no tumor visible on those CT slices --> all good. If margins needed to be tight, we would repeat the same procedure at 1cm above the tumor.
If tumor was visible at 2cm, then we would repeat the process at 3 cm superior to the tumor.
6. Do the same at the inferior margin of the tumor, using CT slices below the inferior margin.

🙂

That sounds ****ing horrible.

4D-CT scan and NEXT PATIENT

 

[Mandelin Rain]

Any comments on central structures? CBD? PV? Even IVC weren't included on 1112 as OARs

 

[evilbooyaa]

Any comments on central structures? CBD? PV? Even IVC weren't included on 1112 as OARs

Only CBD matters. Wouldn't worry about anything venous. Turn down dose in that region to 40/5: Acceptable toxicity after stereotactic body radiation therapy for liver tumors adjacent to the central biliary system - PubMed

 

[Mandelin Rain]

Only CBD matters. Wouldn't worry about anything venous. Turn down dose in that region to 40/5: Acceptable toxicity after stereotactic body radiation therapy for liver tumors adjacent to the central biliary system - PubMed

Right, I think some author have used PV + margin (1-1.5 cm) as a surrogate for biliary tract. Offer some dose/volume criteria. Didn't know how wide accepted that is, as I don't do a ton of liver SBRT.

 

[Mandelin Rain]

Also (somewhat related) ever treated a primary biliary cystadenocarcinoma with SBRT? 2-3 cm. Non resectable.

 

[Ray D. Ayshun]

Getting ready to sim/plan a patient with a 3 cm portal nodal met from CRC (only site of disease on PET and MRI). It appears to be far enough away from bowel to tolerate 5 fx, but I'm wondering if anyone ever applies the 67.5/15 fx type regimen to mets.

 

[Krukenberg]

Getting ready to sim/plan a patient with a 3 cm portal nodal met from CRC (only site of disease on PET and MRI). It appears to be far enough away from bowel to tolerate 5 fx, but I'm wondering if anyone ever applies the 67.5/15 fx type regimen to mets.

Only if the tumor is too big for sbrt. Usually that’s >5cm but sometimes you’d be surprised what your planner can achieve

 

[Ray D. Ayshun]

Only if the tumor is too big for sbrt. Usually that’s >5cm but sometimes you’d be surprised what your planner can achieve

Any rationale with a single nodal met to also treating adjacent nodes electively, akin to IHCC?

 

[thecarbonionangle]

Yea 67.5-70.5/15 is my go to.

 

[seper]

Do you have a CT snapshot? 70/15fx may be too much for other structures in this region

 

[thecarbonionangle]

Do you have a CT snapshot? 70/15fx may be too much for other structures in this region

Depends on location of course and always meet constraints and underdose as needed. need to be confident in your set up and your team. breath-hold if possible.

 

[Ray D. Ayshun]

Do you have a CT snapshot? 70/15fx may be too much for other structures in this region

You mean concern for biliary structures? My impression from reading cranes stuff is greater concern for that with 5 fx than 15.

 

[seper]

You mean concern for biliary structures? My impression from reading cranes stuff is greater concern for that with 5 fx than 15.

yes and also spilling into stomach, duodenum. That is so much more dose than good old 6 Gy X 5

 

[Ray D. Ayshun]

yes and also spilling into stomach, duodenum. That is so much more dose than good old 6 Gy X 5

Large bowel and biliary structures are the only real concern. Other stuffs far enough away. In any case, single site of disease, so intent here is way more aggression than 6 gy x 5. I think 10 x 5 should be doable very safely, but my larger question is wondering about "ENI" in cases like this, for instance 67.5/15 to gross disease and 45/15 to adjacent nodal basin. In hematogenous mets it's pretty easy to stop at the lesion, but when there's an anatomic road these cells are traveling down, it makes me wonder about treating up and downstream a little bit...

 

[thecarbonionangle]

yes and also spilling into stomach, duodenum. That is so much more dose than good old 6 Gy X 5

proximity to mucosal surfaces like stomach, duodenum etc pushes me toward fractionation, usually 15 fractions. you do a PRV crane approach and meet 15 fx constraints. Try to get BED10 near 100

 

[seper]

Large bowel and biliary structures are the only real concern. Other stuffs far enough away. In any case, single site of disease, so intent here is way more aggression than 6 gy x 5. I think 10 x 5 should be doable very safely, but my larger question is wondering about "ENI" in cases like this, for instance 67.5/15 to gross disease and 45/15 to adjacent nodal basin. In hematogenous mets it's pretty easy to stop at the lesion, but when there's an anatomic road these cells are traveling down, it makes me wonder about treating up and downstream a little bit...

Both 10 Gy X 5 and 4.5 Gy X 15 far exceed bowel tolerance, that was I trying to say I guess.
Overal prognosis is poor, anyway

 

[thecarbonionangle]

Both 10 Gy X 5 and 4.5 Gy X 15 far exceed bowel tolerance, that was I trying to say I guess.
Overal prognosis is poor, anyway

The bowel is not getting that though, you respect constraints and give a higher dose where you can, bowel or stomach nearby gets something like 40s/15 per timmerman

 

[seper]

The bowel is not getting that though, you respect constraints and give a higher dose where you can, bowel or stomach nearby gets something like 40s/15 per timmerman

It depends on individual anatomy and final margin. That's why I asked for an image. 400 X 15 may be OK for small volumes of stomach and transverse colon, agree

 

[thecarbonionangle]

I watch my come beams very carefully. Empty stomach and put a 1-2 mm PRV on it. Ive had a few recent bouts of liver mets right by stomach/bowel where i could not get that good of a plan with 5 fractions SBRT and was able to get more dose in while meeting constraints. I think fractionation is your friend in proximity to mucosal surfaces. In my experience, breath-hold can be incredibly helpful in some of these cases.

 

[evilbooyaa]

Getting ready to sim/plan a patient with a 3 cm portal nodal met from CRC (only site of disease on PET and MRI). It appears to be far enough away from bowel to tolerate 5 fx, but I'm wondering if anyone ever applies the 67.5/15 fx type regimen to mets.

You can but this is metastatic disease. We talk about prioritizing OARs in localized cholangio, but do so even more (maybe wider PRV or something) in this scenario. Prioritize not hurting the patient. Solitary site of metastatic disease?

Any rationale with a single nodal met to also treating adjacent nodes electively, akin to IHCC?

I see zero reason to do ENI. This is not stepwise regional lymph node (like a cervical cancer patient who was treated to pelvis who fails in the para-aortics) failure, this is true, no questions asked, M1 failure.

 

[Ray D. Ayshun]

Solitary site of metastatic disease?

If I don't go into this acting as if this is the case, then I'm not sure what I'm doing as there's nothing to palliate.

 

[seper]

If I don't go into this acting as if this is the case, then I'm not sure what I'm doing as there's nothing to palliate.

goes without saying - you are palliating referring's and patient's anxieties

 

[Ray D. Ayshun]

goes without saying - you are palliating referring's and patient's anxieties

Is that because this CRC, or just the general feeling about oligomets? I'm always palliating my need for more stuff as well.

 

[Doctorer]

Getting ready to sim/plan a patient with a 3 cm portal nodal met from CRC (only site of disease on PET and MRI). It appears to be far enough away from bowel to tolerate 5 fx, but I'm wondering if anyone ever applies the 67.5/15 fx type regimen to mets.

Yup, I've done it. It's definitely an edge case, however you have to ask yourself whether what you're doing is really worth it. A portal nodal met is almost certainly not the only site of disease, and treatment is unlikely to be curative. Ablative treatment may put them at an increased risk of toxicity without a benefit, ultimately. Still, uncontrolled portal nodes can lead to complications if they progress, so if you can safely get away with it, and it's really the only site of disease, I might consider it.

 

[seper]

Is that because this CRC, or just the general feeling about oligomets? I'm always palliating my need for more stuff as well.

One way to think about this patient (admittedly extreme): why not have liver surgeon explore her and take the node out? If surgery "not worth it" so is overly aggressive RT.

 

[Ray D. Ayshun]

One way to think about this patient (admittedly extreme): why not have liver surgeon explore her and take the node out? If surgery "not worth it" so is overly aggressive RT.

she's had a couple operations in the past. Always has some post-op complication. This is inoperable inasmuch as the patient is against it.

 

[evilbooyaa]

If I don't go into this acting as if this is the case, then I'm not sure what I'm doing as there's nothing to palliate.

OK, and I get the thought process - patient has one nodal met, what stops them from having nearby nodal metatasis.

I get it. I do. But, still no reason to do ENI here. Yes chances are low with nodal met, but very few things in cancer are zero.

 

[Ray D. Ayshun]

OK, and I get the thought process - patient has one nodal met, what stops them from having nearby nodal metatasis.

I get it. I do. But, still no reason to do ENI here. Yes chances are low with nodal met, but very few things in cancer are zero.

Don't disagree in hindsight re no eni, as it never sounded good, but I was curious to see what all weird stuff people do. Otoh, it is surprising to hear that people think it's okay (not necessarily you) to sbrt a site of disease with no chance of helping anything. Is the oligomet paradigm an empty concept?

 

[evilbooyaa]

Don't disagree in hindsight re no eni, as it never sounded good, but I was curious to see what all weird stuff people do. Otoh, it is surprising to hear that people think it's okay (not necessarily you) to sbrt a site of disease with no chance of helping anything. Is the oligomet paradigm an empty concept?

I meant chances of cure are low. I think chances of improving PFS or time to progression is potentially worthwhile.