Standard vs MRI-based brachytherapy question...

[Radonc90]

I still do standard HDR brachy Point A, point B.
I know this sounds old and historical but the results are great for me.

I have a questions for you guys...

1. How many of you guys do MRI-based brachy?

2. Any data showing MRI is better than standard point A/B?
In other words, MRI will make the isodose better (but higher dose close to the tandem) but:
- any data showing MRI yields better outcome, or is it just showing better isodose and that is it?
- toxicity data?

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[BobbyHeenan]

I very rarely use MRI after the implant. Logistically right now it’s just not very do able - the hospital is working on a 3rd unit but just not available at present.

I do always draw a CTV based upon a CT scan after implant (often PET and MRI fusions though obviously lots of difficulty with errors in fusion ). I scan with a full and emptybladder too to look at bowel (typically treat with full bladder).

I start by looking at point A plan and all the DVHs. If I don’t like coverage or OAR D2ccs we further graphically optimize the plan, and look at Rx’ing to CTV.

Im not as good as the academic pros but I do a good amount of cervix. New Astro guidelines have good dose recs, I keep that document printed off by the brachy computer.

 

[RickyScott]

Regarding data, Akila viswanathan (had a large series at Dfcc with very impressive local control 95%+ using mri and interstitial as needed. I also respect her immensely.

 

[elementaryschooleconomics]

We routinely use MRI after implant but - large academic center, very easy to arrange compared to smaller hospitals or freestanding.

 

[Radonc90]

Oh,

Forgot to say that I can do tandem/Syed template, i.e., mix of tandem and needles if I need to.
Very familiar with it.

It boils down to the basic question: is MRI really that much better, given limitation of inverse square law?

 

[RSAOaky]

Oh,

Forgot to say that I can do tandem/Syed template, i.e., mix of tandem and needles if I need to.
Very familiar with it.

It boils down to the basic question: is MRI really that much better, given limitation of inverse square law?

you don’t necessarily need an MRI to do volume based planning. Your HR-CTV is the whole cervix + GTV. For instances where you’ve had a good response to treatment an MRI doesn’t add much because you can identify the cervix in CT. You can start off the same (prescribing to point A) and adjust the loading so that the HR-CTV is covered which will allow you to spare a bit more than you have been.

 

[seper]

1. Most people use MRI to define targets in 2020. It is trully helpful once you get used to looking at images. The easiest way is to get a diagnostic MR prior to 1st insertion
2. EMBRACE compared to historic data is the evidence that you are looking for. It is believable.

 

[RSAOaky]

1. Most people use MRI to define targets in 2020. It is trully helpful once you get used to looking at images. The easiest way is to get a diagnostic MR prior to 1st insertion
2. EMBRACE compared to historic data is the evidence that you are looking for. It is believable.

I should add that I do get an MRI prior to first insertion. I have tried fusing the two and planning based on the MRI but this approach is only as good as the fusion and the fusion is never convincing so I prefer to just use the CT

 

[FreakFlag]

Why make the jump from 2D point A style to 3D-based brachy?
Short answer - prospective French STIC study showed 3D cervix brachy had better local control and half the toxicity of 2D point-A cervix brachy. Impact of 3D image-based PDR brachytherapy on outcome of patients treated for cervix carcinoma in France: Results of the French STIC prospective study

MRI? ...or CT HDR?
3D adaptive CT-sim cervix HDR is likely sufficient for a lot of cases you'll encounter. Compared to MRI-sim HDR, 3D CT-based HDR is generally faster and less complicated. When you're just starting out, limit your cases to intracavitary FIGO I or early IIB patients. Have your gynonc place a Smit sleeve in the OR near the end of 45Gy, a few days before the first HDR appointment. With this setup you can implant/deliver your 6 or 7Gy fraction start to finish in ~3-4 hours all within your department.

How to transition from 2D to 3D HDR?
Attend the American Brachytherapy Society GYN school with your physicist to learn from the gurus. It's 2-3 great days in Florida...in a conference room. Also consider a field trip to Louisiana to see how efficient 3D CT-based HDR can be done in a busy community setting (real patients): Essentials in Gynecological HDR Brachytherapy - BrachyAcademy

What about advanced patients?
Know your department's limits. For FIGO III or bad IIB patients, strongly consider referring them to a med school where they can receive a proper interstitial HDR boost after 45Gy EBRT in your dept. These patients benefit from implanting with needles in the OR under general, intraoperative transrectal US/Doppler to properly implant parametrial disease and avoid lancing vessels, MRI simulation, experienced physics & brachy nursing, PCA narcotics, and a gynonc/rapid response team next door in case of bleeding out upon interstitial needle removal. HDR'ing parametrial disease beyond point A is favored as more effective and lless toxic than an old-school EBRT parametrial boost.


What could I read during COVID-19 before the conferences resume?

Quick read - ARRO Cliffs notes version of 3D cervix brachy

https://www.astro.org/uploadedFiles/Affiliates/ARRO/Resident_Resources/Educational_Resources/Case_Vingettes/CervicalCancer.pdf

Super detailed read - EMBRACE II cervix protocol

https://www.embracestudy.dk/UserUpload/PublicDocuments/Docs/EMBRACE_II_title_page_and_total_protocol_v15_151015.pdf

ABS references

GYN

GEC-ESTRO (ACROP)–ABS–CBG Consensus Brachytherapy Target Definition Guidelines for Recurrent Endometrial and Cervical Tumors in the Vagina - International Journal of Radiation Oncology, Biology, Physics (redjourna

www.americanbrachytherapy.org

For your physicists - ICRU 89

ICRU

www.icru.org

 

[RickyScott]

Why make the jump from 2D point A style to 3D-based brachy?
Short answer - prospective French STIC study showed 3D cervix brachy had better local control and half the toxicity of 2D point-A cervix brachy. Impact of 3D image-based PDR brachytherapy on outcome of patients treated for cervix carcinoma in France: Results of the French STIC prospective study

MRI? ...or CT HDR?
3D adaptive CT-sim cervix HDR is likely sufficient for a lot of cases you'll encounter. Compared to MRI-sim HDR, 3D CT-based HDR is generally faster and less complicated. When you're just starting out, limit your cases to intracavitary FIGO I or early IIB patients. Have your gynonc place a Smit sleeve in the OR near the end of 45Gy, a few days before the first HDR appointment. With this setup you can implant/deliver your 6 or 7Gy fraction start to finish in ~3-4 hours all within your department.

How to transition from 2D to 3D HDR?
Attend the American Brachytherapy Society GYN school with your physicist to learn from the gurus. It's 2-3 great days in Florida...in a conference room. Also consider a field trip to Louisiana to see how efficient 3D CT-based HDR can be done in a busy community setting (real patients): Essentials in Gynecological HDR Brachytherapy - BrachyAcademy

What about advanced patients?
Know your department's limits. For FIGO III or bad IIB patients, strongly consider referring them to a med school where they can receive a proper interstitial HDR boost after 45Gy EBRT in your dept. These patients benefit from implanting with needles in the OR under general, intraoperative transrectal US/Doppler to properly implant parametrial disease and avoid lancing vessels, MRI simulation, experienced physics & brachy nursing, PCA narcotics, and a gynonc/rapid response team next door in case of bleeding out upon interstitial needle removal. HDR'ing parametrial disease beyond point A is favored as more effective and lless toxic than an old-school EBRT parametrial boost.


What could I read during COVID-19 before the conferences resume?

Quick read - ARRO Cliffs notes version of 3D cervix brachy

https://www.astro.org/uploadedFiles/Affiliates/ARRO/Resident_Resources/Educational_Resources/Case_Vingettes/CervicalCancer.pdf

Super detailed read - EMBRACE II cervix protocol

https://www.embracestudy.dk/UserUpload/PublicDocuments/Docs/EMBRACE_II_title_page_and_total_protocol_v15_151015.pdf

ABS references

GYN

GEC-ESTRO (ACROP)–ABS–CBG Consensus Brachytherapy Target Definition Guidelines for Recurrent Endometrial and Cervical Tumors in the Vagina - International Journal of Radiation Oncology, Biology, Physics (redjourna

www.americanbrachytherapy.org

For your physicists - ICRU 89

ICRU

www.icru.org

Gave this up years ago. It really should be done by someone who is performing a few cases a month, probably not more than 1-2 radoncs per major metro

 

[FreakFlag]

Nice 2014 survey on cervix brachy trends in the US

Image Guided Cervical Brachytherapy: 2014 Survey of the American Brachytherapy Society - PubMed

Although use of image-based brachytherapy has increased in the United States since the 2007 survey, there is room for further growth, particularly with the use of MRI. This increase may be in part due to educational initiatives. However, there is still significant heterogeneity in brachytherapy...

pubmed.ncbi.nlm.nih.gov

• 46% were still planning to point A.
• 52% were using 3D volume-based (e.g., planning to HR-CTV D90).
• 34% were using MRI.

3D CT technique is sufficient for HDR target delineation in early disease, but MRI planning is recommended in advanced disease:

Computed tomography versus magnetic resonance imaging-based contouring in cervical cancer brachytherapy: results of a prospective trial and preliminary guidelines for standardized contours - PubMed

Computed tomography-based or MRI-based scans at brachytherapy are adequate for OAR DVH analysis. However, CT tumor contours can significantly overestimate the tumor width, resulting in significant differences in the D(90), D(100), and volume treated to the prescription dose or greater for the...

pubmed.ncbi.nlm.nih.gov

Comparison of Computed Tomography- and Magnetic Resonance Imaging-based Clinical Target Volume Contours at Brachytherapy for Cervical Cancer - PubMed

We recommend MRI-based brachytherapy planning for patients with tumors >5 cm and parametrial invasion on MRI at diagnosis and for those with a high BMI.

pubmed.ncbi.nlm.nih.gov

 

[Radonc90]

Thanks all,

I have done > 250 HDR cases (T&O or Tandem + needles) over the years, I am familiar with the pros and cons.
I just wonder what MRI brings to the table.

 

[MegaVoltagePhoton]

Mri just gives a much better picture. Like agood cervix mri is a work of art for me. Call me a sucker for stic and embrace but I think using an mri here will allow lower toxicity and more local control

 

[RadRadRad]

Thanks all,

I have done > 250 HDR cases (T&O or Tandem + needles) over the years, I am familiar with the pros and cons.
I just wonder what MRI brings to the table.

The links in the long post are useful. Multiple articles show 50% reduction in high grade toxicity. I trained at a place that did 2D to point a. I was fortunate to end up in a practice that already had mri guided up and running and have been doing this for years. The doses to critical structures are notably less. I understand you might be able to breathe something similar with ct based planning but I like being able to see how much disease is left outside the cervix for the IIb and IIIb cases and this is only possible with mri.

for what it’s worth article several years ago showed how just slight alterations in mri fusion could lead toinadequate coverageespecially for locally advanced patients. Highly recommend mri compatible applicator and getting mri withapplicator in place if logistically possible.

 

[ramsesthenice]

Thanks all,

I have done > 250 HDR cases (T&O or Tandem + needles) over the years, I am familiar with the pros and cons.
I just wonder what MRI brings to the table.

There are 2 potential issues here related to imaging: Are we talking about 2D vs 3D or diagnostic CT vs MRI? There is a mountain of data showing less toxicity with 3D vs 2D referenced above. There is a very poor correlation between ICRU reference points and volumetric references like D2cc. 3D also gives you more opportunity to account for a suboptimal implant than 2D. When performing 3D we always start by generating a point A plan and then tweaking it to minimize normal tissue dosing while maintaining sufficient HRCTV coverage. If everything is rosy with the PtA plan then I go with it but that is at most 10% of the time.

CT vs MRI is a bit more subtle. I think a major factor that weighs into MR vs CT is when you start your implants. There is a push among groups like EMBRACE to start HDR earlier and interdigitate with the EBRT. Why am I mentioning this? Because the earlier in treatment that you start treating the more likely it is that your patient will have extracervical extension. MRI is much better at identifying disease extension to the parametria, vagina, and uterine corpus than CT. For patients without extracervical disease it is generally pretty easy to accurately contour the HRCTV with CT only and I myself frequently do use CT-based planning for these patients. However, even in this population MRI can still be helpful in some instances by defining the GTV. If you are fighting between target and avoidance dosing it is helpful to know where on the HR-CTV you can cheat a bit and still maintain adequate D90 coverage. I always get an MRI on fraction 1 but if it isn't helpful I stick to CT for the remaining fractions.

FWIW I still do some 2D plans too from time to time. Generally for morbidly obese patients that surgery declines to operate on who are also too big for any of our scanners. Sadly, this is not a super rare occurrence.

I see where you are coming from but this is a bit tricky. Personal experience is a bit limited because no matter how you treat patients outcomes are highly variable. Bad things can happen with perfect plans and (fortunately) people can do just fine with otherwise horrifying plans. Large data sets like those from EMBRACE are going to be needed to really appreciate differences in outcomes.

 

[evilbooyaa]

Thanks all,

I have done > 250 HDR cases (T&O or Tandem + needles) over the years, I am familiar with the pros and cons.
I just wonder what MRI brings to the table.

I am now assuming that you are talking about doing CT-based planning. But even then, you really shouldn't be prescribing to point A or H anymore, but rather HR-CTV. HR-CTV coverage (D90) > EQD2 of 85Gy is a major predictor of local control per EMBRACE and retroEMBRACE data.

Definitely for anybody with parametrial extension, MRI is much better than CT at delineating the extent of disease vs contouring normal parametria as part of HR-CTV.

Even for cervix only disease, the HR-CTV contour shrinks a little bit with MRI vs CT only based planning. Meeting dose constraints D2 rectal and bladder while is easier when HR-CTV is smaller.

In terms of increasing toxicity:

MRI-based planning to HR-CTV < CT-based planning to HR-CTV << CT-based planning to point A <<<<<<<< 2D-based planning to point A