Daily imaging poll

[xrthopeful]

Just want to get a sense of what kind of patients people are doing daily CBCT for when doing IMRT.

Head and neck seems standard, CNS, prostate patients. Do you guys standardly do for all lung patients?

When you are doing daily CBCT, do you guys get any other 2d images on any of the fractions?

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[Mandelin Rain]

I try to do CBCT when treating most anything but breast, bone, and or whole brain. Sometimes payors have other ideas.

If I'm contouring soft tissue and targeting soft tissue, I want to be localizing to the same soft tissue.

 

[xrthopeful]

And when you are doing CBCT, you don’t also have your therapists do a KV prior, correct

 

[Neuronix]

Our therapists often do a quick kV before the CBCT to make sure they're in the right ballpark if there's any question about misalignment. That saves us from doing multiple come beams for positioning. The kVs usually get deleted so I don't have extra films to review every day. We only bill for the CBCT. I'm pretty sure you can't bill for both anyway.

Whether you want to review all the images is up to you, but I usually only do that for the first fraction.

As to which to pick and for which body site, depends on situation for me. Lung is one of those borderline areas. For conventionally fractionated, if the CTV and PTV are large like 7 mm each or so, you don't need a daily CBCT. If you're reducing your PTV due to target size or whatever, you need CBCT daily to ensure position.

I personally prefer CBCT for most targets where daily IGRT is indicated except some simple or bony targets or when I'm using MRI guidance. The extra radiation dose is low nowadays to my understanding and they're fast and easy to get on modern machines.

 

[Mandelin Rain]

As stated above, they may take a kV to get in the area. Certainly on the first day. If there isn't a big shift off tattoo, they usually don't have to daily.

 

[KHE88]

Only thing I cone beam for every treatment is SBRT.

Prostate, lung, head and neck, gyn, etc IMRT. CBCT once a week and kV daily.
Breast ports every 3 days.

Walked into a new practice where they were cone beaming every day and it was frustrating. Unless you're going to the machine to check the cone beam prior to every treatment, what's the point? Just extra dose for no reason. Over a conventional prostate course that can add up to an extra fraction of treatment.

 

[Neuronix]

Over a conventional prostate course that can add up to an extra fraction of treatment.

Do you have data for this? What I remember is that's for older generation imagers, especially MV CT/CBCT. I could be wrong though.

 

[Mandelin Rain]

I glean a lot of information from cone beams. Adequacy of bladder filling. Rectal changes. Is the small bowel loop falling into the pelvis? Has the head and neck patient lost too much weight (contours going outside the skin)? Did the lung open back up? Is the tumor shrinking?

Most importantly, am I hitting the right spot?

 

[Neuronix]

Well for conventional prostate you've got fiducials, CBCT, and/or old school doses with large PTVs. Fiducials aren't exactly totally benign either. Something like 1.5% hospitalization rate for infection is what I hear.

 

[KHE88]

Do you have data for this? What I remember is that's for older generation imagers, especially MV CT/CBCT. I could be wrong though.

Fair enough, I'll step that back. You hear that a lot, but I did look it up and with modern imagers daily cone beams would result in a total extra dose of 5 cGy or less over the treatment course.

Still think you need a good reason to do it. Why would you cone beam a head and neck daily? Are you doing 6 DOF corrections over 30 fractions? Weekly is enough to assess tumor response and anatomical changes.

 

[Mandelin Rain]

Still think you need a good reason to do it.

Why?

Isn't seeing the tumor and OARs in the right spot each day a good enough reason?

Is looking at bones better in some way, or is it worse?

 

[Neuronix]

I think either is reasonable for H&N--daily or weekly.

Though you brought up an interesting point. I treat a lot of crazy base of skull tumors. Yes we do CBCT and 6D couch shifts for every fraction. Therapists use auto match and it's really damn good if the auto match volume is correct. I use 2 mm PTV sometimes in these cases.

You can only do that in the brain/skull (not H&N with LN regions) because of neck flexion/extension. You need at least 3 mm (some argue 5 mm) to match over a long volume given the non-rigid setup errors for H&N. I don't think 6D is as useful in those cases for that reason--3D with kV or CBCT gets you close enough.

 

[medgator]

Only thing I cone beam for every treatment is SBRT.

Prostate, lung, head and neck, gyn, etc IMRT. CBCT once a week and kV daily.
Breast ports every 3 days.

Walked into a new practice where they were cone beaming every day and it was frustrating. Unless you're going to the machine to check the cone beam prior to every treatment, what's the point? Just extra dose for no reason.

Financially toxic as well....cbct pays 40-50% more in the freestanding setting than kv igrt

 

[Neuronix]

IMO, reimbursement is the biggest reason CBCT took off. If MRI gets its own higher paying guidance code, everyone will want an MRI guided unit. Environment isn't favorable for that right now, but who knows in the future...

 

[Mandelin Rain]

I have literally no idea what I get reimbursed to check a CBCT vs kVkV. The difference may be 40%, but I think in absolute terms that 40% is quite small. Like <$10.

I like CBCT because it is prima facie a better way of localizing most tumors/OARs. For bone kVkV is superior IMO, so I order that. For breast, ports work fine because you're basically treating a contour.

 

[medgator]

I have literally no idea what I get reimbursed to check a CBCT vs kVkV. The difference may be 40%, but I think in absolute terms that 40% is quite small. Like <$10.

I like CBCT because it is prima facie a better way of localizing most tumors/OARs. For bone kVkV is superior IMO, so I order that. For breast, ports work fine because you're basically treating a contour.

I meant it on the technical side, I doubt the professional is as big a discrepancy.

I use kVs IGRT for my pts getting a breast boost and that seems to be the only thing evicore approves in breast unless you are treating 4 field

 

[deleted1002574]

CBCT for almost everything- except breast and whole brain.

I wish there was minimal reimbursement or bundling. It’s not about money. If I have an ability to see things, I’d like to use it.

 

[deleted18755]

I try to do CBCT when treating most anything but breast, bone, and or whole brain. Sometimes payors have other ideas.

If I'm contouring soft tissue and targeting soft tissue, I want to be localizing to the same soft tissue.

When you say payers have other ideas do you mean they won't allow CBCT but would allow KV imaging, or they reject IGRT altogether? Just curious.

I have had to argue for daily IGRT vs weekly portal imaging of course but have never been "told" to do KV instead of CBCT . . . am I just "lucky?"

 

[KHE88]

Patient-specific three-dimensional concomitant dose from cone beam computed tomography exposure in image-guided radiotherapy - PubMed

The additional dose from on-line IGRT procedures can be clinically relevant. The organ dose can be significantly reduced with the use of appropriate patient-specific settings. The concomitant dose from CBCT should be accounted for and the acquisition settings optimized for optimal IGRT...

www.ncbi.nlm.nih.gov

"In the pelvis, a single CBCT scan delivered a mean dose to the femoral heads of 2-6 cGy and the rectum of 1-2 cGy. An additional dose to the planning target volume was within 1-3 cGy. In the chest, the mean dose to the planning target volume varied from 2.5 to 5 cGy. The lung and spinal cord planning organ at risk volume received ≤4 cGy and ≤5 cGy, respectively."

5 cGy * 44 fractions = 220 cGy

That's a little more than the 1000 microsieverts or so the manufacturer states per scan.

Radiation dose from cone beam computed tomography for image-guided radiation therapy - PubMed

Patient position verification by standard mode CBCT acquired by OBI on a daily basis could increase the secondary cancer risk by up to 2% to 4%. Therefore lower mAs settings for daily CBCT should be considered, especially when bony anatomy is the main interest.

www.ncbi.nlm.nih.gov

"Patient position verification by standard mode CBCT acquired by OBI on a daily basis could increase the secondary cancer risk by up to 2% to 4%."

"The effective doses to the body from standard mode CBCT for imaging of head and neck, chest, and pelvis were 10.3, 23.7, and 22.7 mSv per scan, respectively."


So yeah, low risk but not zero risk and needs good justification.
Points about increased technical costs are also well-taken.

 

[evilbooyaa]

Any IMRT gets daily CBCT. Head and neck, lung, palliative, whatever. KV generally at first fraction to confirm shifts are not excessive and avoid having to repeat CBCT.

No CBCT in patients not getting IMRT unless physician-requested.

No daily kV in patients not getting IMRT unless physician-requested. Breath hold for L breast cancer, those get daily MV ports.

Otherwise MV ports once a week for patients not getting IMRT.

In regards to frequency of prostate IGRT:

Daily Versus Weekly Prostate Cancer Image Guided Radiation Therapy: Phase 3 Multicenter Randomized Trial - PubMed

Compared with weekly control, daily IGRT control in prostate cancer significantly improves biochemical progression-free and clinical progression-free interval, and rectal toxicity.

www.ncbi.nlm.nih.gov

Improved prostate cancer control with daily imaging. Worse OS in the daily imaging group, due to secondary cancer risks, but most of the secondary cancer discrepancy was outside of the pelvis area and not hematological. In practice as an attending I'll think about the frequency of it for younger patients getting say lung, but I shrink margins quite a bit in lung and H&N compared to standard guidelines, so I don't see myself changing it.

 

[medgator]

For patient throughput, I do kv with fiducials on prostates with cbct weekly to confirm bladder filling before tx

 

[RickyScott]

I try to do CBCT when treating most anything but breast, bone, and or whole brain. Sometimes payors have other ideas.

If I'm contouring soft tissue and targeting soft tissue, I want to be localizing to the same soft tissue.

Yes, you are going to catch most mistakes this way. If I don’t do CBCT, I always do kv orthog or vision xrt/ surface guidance. You won’t get anything close to sigma 6 setup errors/failure to shift etc without some type of daily image guidance.

 

[scarbrtj]

No MD is going to the machine for daily checks of either CBCT or kV. Thus, one of two things are happening: software-based shifts or therapist-based shifts. Therapist-based shifts are a bad idea. You can take a slew of unidimensional therapist-based shifts and are likely to discover mean shifts >1mm indicating systematic error. Systematic error is way worse than random error; e.g., in one recipe PTV margin equals 2.5*S+0.7s where S=systematic error and s=random error. Software-based shifting is much less prone to systematic error and also will have less random error. (Unidimensional shift values take a bell-shaped curve distribution and their mean over a large population should always be near 0mm; if not, it's systematic error... the std dev's of the shifts are the random error.) Software-based CBCT matching offers the lowest amount of systematic and random error. Next time you're at the machine, do a kV match and a CBCT match. You are apt to find a mm or, or greater, difference in the unidimensional shift values. Which method offers the "truth"? Which one is correct? Which one will you match to? Actually these questions can be answered mathematically. In any match whether CBCT or kV, there is one point in space which can be perfectly matched. All points emanating outward from that singularity are imperfectly matched. And worrying about CBCT radiation exposure is sort of like worrying about how much opossum farts contribute to global warming. (One caveat: actually kV fiducial based matching offers the lowest random and systematic error; CBCT can offer similar levels but obv kV quicker, easier, cheaper.)

 

[medgator]

. (One caveat: actually kV fiducial based matching offers the lowest random and systematic error; CBCT can offer similar levels but obv kV quicker, easier, cheaper.)

Cbct let's you check whether your pts are filling their bladder prior to tx. It's why I do it periodically, but otherwise prefer kv with fiducials in prostate ca daily

 

[deleted1002574]

Cbct let's you check whether your pts are filling their bladder prior to tx. It's why I do it periodically, but otherwise prefer kv with fiducials in prostate ca daily

Not unreasonable, but then why do periodically if you do feel bladder filling matters? Wouldn't you just do it daily?

I would presume if doing kV daily and you do care about bladder filling, you'd do an ultrasound daily. If you don't care about it, then kV daily seems fine. Otherwise CBCT seems to check both boxes. My gut says, if you care about image guidance, then do image guidance properly.

(There is a lot of practice variation, just curious as to rationale)

 

[medgator]

Not unreasonable, but then why do periodically if you do feel bladder filling matters? Wouldn't you just do it daily?

I would presume if doing kV daily and you do care about bladder filling, you'd do an ultrasound daily. If you don't care about it, then kV daily seems fine. Otherwise CBCT seems to check both boxes. My gut says, if you care about image guidance, then do image guidance properly.

(There is a lot of practice variation, just curious as to rationale)

Weekly is something we've gotten accustomed to in the clinic. Pts can usually subjectively tell after a couple of cbcts how full they need to be. I

Are you at the console all day checking all those cbcts 5 days a week? We realistically can't do that

 

[xrthopeful]

Why do you need to be at the console to check the cbct? Review and approve at the end of the day and make suggestions for the next day if needed

 

[medgator]

Why do you need to be at the console to check the cbct? Review and approve at the end of the day and make suggestions for the next day if needed

It's been our Dept policy to review cbcts at the tx console. Some of the therapists probably feel comfortable enough to line up fiducials on a cbct but not bladder and rectal positioning and fullness which imo would be the point of doing it every day in prostate.

I.e., they wouldn't be able to tell if the pt needed to drink more water, although some of them figure it out better than others.

Plus the daily dose concerns, financial toxicity etc. I only do cbct daily every fx if someone can't get fiducials, or in situations like hypofx lung, sbrt etc

 

[scarbrtj]

Not unreasonable, but then why do periodically if you do feel bladder filling matters? Wouldn't you just do it daily?

I would presume if doing kV daily and you do care about bladder filling, you'd do an ultrasound daily. If you don't care about it, then kV daily seems fine. Otherwise CBCT seems to check both boxes. My gut says, if you care about image guidance, then do image guidance properly.

(There is a lot of practice variation, just curious as to rationale)

The kV image is really super-choicy for showing the fiducials and their spatial arrangement. Can't be beat by CBCT IMHO. Easier to hit that "center of mass" for the seeds with kV. Although in theory you can drop match points on CBCT etc. Be that as it may, what *I* do is CBCT to ensure bladder and rectum not massively distended/empty vs sim. I accept a lot of leeway here and that is therapist's judgment call. Then we kV and match/shift to seeds after the "rough" CBCT shift. Which usually it's just a couple mm at most but still the fiducials are highly reliable w/ almost zero intrauser (user=therapist) variability. Prostate is only situation where I routinely use fiducials and thus only routine kV situation for me. Else, I'm CBCT exclusively when IGRT'ing.

 

[FrostyHammer]

Does anyone do daily CBCT with fiducials in place? I've known multiple rad oncs who do this for all patients and it's infuriated me... Although not as much as the *****s who did CBCT for breast boosts.

 

[deleted1002574]

Does anyone do daily CBCT with fiducials in place? I've known multiple rad oncs who do this for all patients and it's infuriated me... Although not as much as the *****s who did CBCT for breast boosts.

Why does it infuriate you?

You think that people that do that are *****s?

I’m not sure why to repeat myself, but if you are looking at both bladder filling / rectal volume AND the prostate, then there is not a better single modality than CBCT, currently (MRI for a few centers). If payors want to bundle that, it’s fine. KV can only see prostate. US can see both bladder and prostate, but not very well.

It is a standard of care (not THE standard, but A standard) to use CBCT daily.

Another reason why this field is on downswing is because of the constant maligning of other physician’s practice by those less experienced or younger (or both). There is no field where this is so widespread. Check any forum. Blame the academics for the residency spots, but I’ll blame all of you below me for maligning me and my elders constantly and consistently.

There is such thing is variation of practice and malpractice. Please be able to note the difference.

I would love for IGRT to just be bundled for all treatments. I care not at all about the money. I just like to be able to see and adjust. What’s the downside?

 

[medgator]

Another reason why this field is on downswing is because of the constant maligning of other physician’s practice by those less experienced or younger (or both). There is no field where this is so widespread. Check any forum. Blame the academics for the residency spots, but I’ll blame all of you below me for maligning me and my elders constantly and consistently.

There is such thing is variation of practice and malpractice. Please be able to note the difference.

Goes both ways. Heard a lot of maligning from the "elder" partners when I first got out of training, although to be fair, it was a malignant group.

Agree it did not warrant the "*****" description.

I personally don't have a comfort level with my therapists, nor machine time to do cbcts daily on most of my patient load, so weekly it is for me on most things outside of sbrt

 

[scarbrtj]

Does anyone do daily CBCT with fiducials in place? I've known multiple rad oncs who do this for all patients and it's infuriated me... Although not as much as the *****s who did CBCT for breast boosts.

You've got a lot of letters to the editor to write regarding the infuriating CBCT habits of a lot of *****s.

 

[SneakyBooger]

From The MedNet:

 

[deleted1002574]

About 40% of radoncs practice in an infuriating way! And perhaps they are *****s.

#WeTheMorons

 

[Neuronix]

If you do CBCT + fiducials, the therapists can align to fiducials, and if they're trained appropriately check bladder and rectal filling on that scan. Worst case you can check bladder and rectal filling later when you do film review and flag it to have MD called before treatment the next day.

If you align to prostate every day with CBCT, your therapists MUST know what they're aligning to. I've seen all sorts of shenanigans when it comes to geriatric rad oncs giving prostate RT. For example, I once saw a practice using CBCT alone giving dose escalated prostate RT with limited PTV where the therapists were happily aligning to the pelvic bones because they didn't know any better. I noped the hell out of there.

I personally think that therapists can be trained for CBCT guided prostate and held to standards (with supervision), but that's not the case in all practices. If so, CBCT+fiducials makes a lot of sense to me because it's simpler. That assumes you care about bladder and rectal filling--if not daily kV with fiducials is faster and simpler (this is the typical urorads setup).

 

[xrthopeful]

I defintiely understand medgator's point about comfort level with therapists, throughput on the machine, etc

However, am I being too naive in not feeling that the daily dose is a concern? With modern CBCT, shouldn't this be a non-issue?

 

[ramsesthenice]

There is no question that CBCT gives you additional information you just can’t get from KV portal imaging, like bladder and rectal filling. I would wager up to 10-15% of the time I have to work on coaching prostate and GYN patients to address consistency issues and keep dose to OARs down. There is also little to no doubt that if most of us were on the table we would want out doc using as much info as possible if they are supposed to be using technology that is accurate within a couple mm.

That being said, the technical fees are not insignificant. It doesn’t directly affect the patient that much since the overall costs have blown past most plan maximums. But, of course, the cost is passed on to everyone else. So does the cost justify the ends if 80+% of the time it doesn’t end up adding anything or altering the treatment plan? I would bet at least half the time I work on someone’s rectal filling they wouldn’t have any clinical consequences if I had overlooked it.

it’s not popular for many reasons, but I am personally an advocate for diagnosis based payments. Prostate IMRT reimburses $X. pick whatever dose-fractionation or imaging you feel is best for the patient. You will get the same payment either way. I realize there are tons of issues with this approach but the IGRT dilemma is a great example of the possible benefits.

 

[medgator]

it’s not popular for many reasons, but I am personally an advocate for diagnosis based payments. Prostate IMRT reimburses $X. pick whatever dose-fractionation or imaging you feel is best for the patient. You will get the same payment either way. I realize there are tons of issues with this approach but the IGRT dilemma is a great example of the possible benefits.

The freestanding community is the one that pushed for bundled payments first before Astro got on board and has tried to take credit. This is what APM is trying to get towards.

There is a lot of support for it now imo, to address things like this as well as over fractionating, and hopefully to stop hospitals and nci designated cancer centers for getting paid more for the same exact service.

 

[FrostyHammer]

Why does it infuriate you?

You think that people that do that are *****s?

I’m not sure why to repeat myself, but if you are looking at both bladder filling / rectal volume AND the prostate, then there is not a better single modality than CBCT, currently (MRI for a few centers). If payors want to bundle that, it’s fine. KV can only see prostate. US can see both bladder and prostate, but not very well.

It is a standard of care (not THE standard, but A standard) to use CBCT daily.

Another reason why this field is on downswing is because of the constant maligning of other physician’s practice by those less experienced or younger (or both). There is no field where this is so widespread. Check any forum. Blame the academics for the residency spots, but I’ll blame all of you below me for maligning me and my elders constantly and consistently.

There is such thing is variation of practice and malpractice. Please be able to note the difference.

I would love for IGRT to just be bundled for all treatments. I care not at all about the money. I just like to be able to see and adjust. What’s the downside?

Yikes, talk about being triggered. Perhaps we just have good therapists who have zero issues aligning to prostate without fiducials. Perhaps it's because many in this forum still are in denial about hypofrac (good luck with that) and want to hang onto every bit of the past as possible. Perhaps it's my specific view that doing it in itself doesn't infuriate me, but if you read my post above, doing it *for all patients* mindlessly does so. Thankfully, the majority of MedNet survey participants don't do both (both was only a plurality). Perhaps don't jump to conclusions by assuming that I think people are *****s for doing both (that word only referred to breast CBCT, which got no pushback this far), and maintain proper decorum on this forum.

 

[scarbrtj]

Yikes, talk about being triggered. Perhaps we just have good therapists who have zero issues aligning to prostate without fiducials.

I'm assuming you literally mean the therapists have no problems w/ CBCT alignment vs software automated shifts. If you wanna get a tad uncertain about how certain therapist shifts are, go to the machine one day. Run a CBCT. Have therapist A (T-A) do his visual/manual shift while therapist B (T-B) is blind to the shift; record T-A's x/y/z (x1/y1/z1) shift. Reset to zero, let T-B do his de novo shift and record x/y/z (x2/y2/z2). Calculate how far apart (A) these shifts are in space per match: A=[(x1-x2)^2+(y1-y2)^2+(z1-z2)^2)]^0.5. Do this like across fifty fractions, maybe 2 or three day's worth of shifting, all kinds of disease sites. If therapists have literally zero issues, A≤1mm for 100% of shifts/matches. (And, mean of all unidimensions should be ≤1mm; if it's not, there are significant problems.) It would be nice if A≤2mm 95+% of the time. It's not. What you will find if you do this little experiment is that A>5mm about 25% of the time, and up to 50% of the time or more. Which is to say, your therapists would agree on the shift-to points being with 5mm of one another maybe only 3 out of 4 shift matches. I just don't think rad oncs truly know how "good" their therapists are at shifts (and "good therapists" re: IGRT and "zero issues" is not a wholly definable thing) unless they've collected a bunch of data and analyzed it. You can't even get MDs to agree on what to contour... and contouring is, if you use your imagination a bit, a form of image guidance. You think intratherapist image guidance agreement will be highly homogenous?

And I definitely would give pushback against CBCT in breast being *****ic. IGRT's sole purpose and sole use is to increase treatment accuracy. (Image-based gating is a different discussion re: accuracy/precision.) It's also a QA for the setup and has safety aspects too: it's virtually impossible to wrong-site or wrong-patient treat w/ daily IGRT so it would be protective against that form of malpractice. So whenever one is using IGRT whether weekly MV X-rays (that's IGRT too), daily kV, or daily CBCT, it's to increase accuracy. It's a recognition that there is always, to some degree, a spatial discrepancy between the "aim point" in the plan and from sim and "aim point" IRL day-to-day on the table. So users of daily volumetric imaging probably just want to increase treatment accuracy; and if I were getting some RT, even to my breast, I wouldn't mind some heightened level of accuracy. AFAIK, there's gotta be a CBCT at every fraction w/ Tomotherapy... and eventually we may one day be doing MRI with every fraction, even palliative cases.

 

[xrthopeful]

Anyone: 1+1 = 2

Scarbrtj: well, actually......

 

[deleted1002574]

No problem. Wasn’t sure which set of colleagues were being referred to as *****s.

 

[scarbrtj]

Anyone: 1+1 = 2

Scarbrtj: well, actually......

Ha. You got me. Yes sometimes things are self-evident, and 1 plus 1 can and does equal 2. But a computer scientist would say 1+1=10. You can add 1+2+3+4+5....∞ and the answer is -1/12. The universe is counter-intuitive.

 

[BobbyHeenan]

I do a fair amount of prostate hypofrac with 70/28 with CBCT without fiducials. We did this is in training routinely. No doctor went to the linac.

When I got to the practice ~6 years ago I had to spend a lot of time with the therapists training them and now they do a good job, but there is a learning curve. I like the CBCT to get a look at bladder filling and rectum too (and sometimes a "floppy sigmoid" that comes down low if bladder filling less than ideal), because sometimes your fiducials can be dead on, but a pocket of air in rectum can be making some deformation issues. I don't trust patients for how their bladders "feel" full too.

I've also been amazed at how many guys have significant calcifications in their prostate too. Those can be contoured and used as "fiducials" on a CBCT. For instance, if I'm doing daily CBCT and a high risk guy has a ton of calc's on his staging CT scan, then I definitely feel comfortable without fiducials.

Overall though, (like coverage of IM's in breast cancer), I find it hard to be dogmatic about fiducials and imaging for prostate cancer. It cracks me up that so many people think there's only one way to do it.

 

[Palex80]

We do CBCT for the first 5 fractions of any VMAT/IMRT plan. Then we switch to two times per week after adjusting the couch shift to the mean value of the first 5 fraction-shifts, unless there were major shifts over the first 5 days. In that case, we will do CBCT "as necessary", perhaps even daily, if shifts remain an issue.

There are exceptions to this rule:
- Any stereotactic treatment --> daily CBCT
- Prostate-RT with fiducials --> daily CBCT
[Concerning the debate over portals vs. CBCT for prostate with fiducials, I find CBCT still superior to fiducials for the simply reason that I have information on bladder and rectal filling with CBCT, which I don't have with portals. My calculated DVHs may be totally wrong, if the filling of these organs changes over time. This has become more of an issue now with hypofractionated treatments. In the past, without CBCT, we re-simed the patients 2-3 times over the course of their 8-week treatment to check on rectal and bladder filling. With hypofractionation, you would have to resim practically every week...]
- Tight margins or high dose next to critical OAR or a prior irradiation in the same/adjacent area with risk of overdosing some critical structure --> daily CBCT

We treat >90% with VMAT.

 

[w00tz]

Having rotated at several sites in residency and now in practice, I have worked with a lot of therapists in the past couple years. There are definitely therapists that I know I can trust more than others. In the practice I joined, we do a lot of CBCTs. Daily for prostate, lung, H&N. For prostates, we use it to look at bladder and rectum size and prostate position. We've train the therapists what to look for and then we review images at the end of the day. If they have a question, they will call us to the console before treating. In our metro, there's oversaturation of radiation therapists (and rad oncs), so we don't have any problems finding therapists we can train and trust and letting go of ones that can't get with the program.

 

[seper]

Where I work, modus operandi is daily CBCT on everything, including palliation. Physician compensation model is without doubt plays the role. I try to limit exposure from excessive CBCT's for curative-intent young patients.

 

[medgator]

daily CBCT on everything, including palliation.

And I felt bad for even thinking about kVing my whole brain pts....

 

[evilbooyaa]

Overall though, (like coverage of IM's in breast cancer), I find it hard to be dogmatic about fiducials and imaging for prostate cancer. It cracks me up that so many people think there's only one way to do it.

This is the right answer to this question and the amount of discussion and calling of *****s for not doing it per one's personal dogma is a serious issue of our field.

I will say that for anything that is not SBRT (MD review prior to every tx) or the first treatment of IMRT (MD review prior to tx req'd) all CBCT review is done at the end of the day. I am not going to the machine every day for 35 fractions for a H&N plan. That is not necessary.