Why are VMAT/IMRT breast plans not common?

[Anthodite]

Is this an insurance thing or a lack of research thing? I only went to one center that’s done most of the time for CW/Whole breast irradiation and seem to do mostly regular 3DCRT tangents. What’s the reasoning for this? Is there like a certain criteria for this?

I have no idea if it’s because the center that did the VMAT/IMRT breasts had patients that typically had expanders in.

I know most places do IMRT/VMAT APBI(at least in my area) but I’m not referring to that here. Despite being mediocre at dosi I know my dose distributions I promise.

I’m a radiation therapy student and I’m horrified of approaching the rad onc. Really would appreciate your guys’ help here.

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[Gfunk6]

We appreciate your questions - the answer is a bit complicated:

1. Historically IMRT has not been covered by insurance companies as they view it as expensive and uncessary. However, in certain scenarios, especially where the left breast is close to the heart or you are treating a lot of lymph nodes, IMRT may be worth it to spare heart.

2. ASTRO used to have avoiding IMRT for breast as one of their "Choose Wisely" guidelines, but have since rescinded this.

3. IMRT can techincally be delivered by two tangent beams by using a complex field-in-field design. This is frequently derided by detractors as "poor man's IMRT" and they feel it should be 3D.

4. IMRT is not always better, even when you think it should be. For instance, if you have a breast patient where you are treating a bunch of lymph nodes and try IMRT, you may find that a lot of low-moderate dose ends up in places you don't want like lung.

 

[Anthodite]

We appreciate your questions - the answer is a bit complicated:

1. Historically IMRT has not been covered by insurance companies as they view it as expensive and uncessary. However, in certain scenarios, especially where the left breast is close to the heart or you are treating a lot of lymph nodes, IMRT may be worth it to spare heart.

2. ASTRO used to have avoiding IMRT for breast as one of their "Choose Wisely" guidelines, but have since rescinded this.

3. IMRT can techincally be delivered by two tangent beams by using a complex field-in-field design. This is frequently derided by detractors as "poor man's IMRT" and they feel it should be 3D.

4. IMRT is not always better, even when you think it should be. For instance, if you have a breast patient where you are treating a bunch of lymph nodes and try IMRT, you may find that a lot of low-moderate dose ends up in places you don't want like lung.

Thank you so much! I just realized how loaded of a question that was. I really appreciate the way you broke it down so well. I didn’t know or realize most of this. Thanks again!!

 

[TheWallnerus]

Not a loaded question at all. Google “twitter breast IMRT.”

IMRT is the standard of care for all early stage breast cancer whole breast RT (including two field tangent step and shoot with segments, and two field tangent inversely optimized sliding window IMRT) with proven less toxicity.*

*evidence based statement

 

[Palex80]

For comprehensive nodal irradiation:

For breast only:

For boosts:

For partial breast:

VMAT FOR...

Disclaimer: Posted already 2 years ago.

Breast IMRT Choosing Wisely... We Knew Ye

Pour one out for ASTRO's Breast IMRT Choosing Wisely. (Ed. note: Love the "recently published evidence" proviso and the past exonerative tense usage.) I believe this is the first ever "withdrawn" Choosing Wisely. Sept 2013: July 2022:

forums.studentdoctor.net

 

[Ray D. Ayshun]

For comprehensive nodal irradiation:

For breast only:

For boosts:

For partial breast:

VMAT FOR...

Disclaimer: Posted already 2 years ago.

Breast IMRT Choosing Wisely... We Knew Ye

Pour one out for ASTRO's Breast IMRT Choosing Wisely. (Ed. note: Love the "recently published evidence" proviso and the past exonerative tense usage.) I believe this is the first ever "withdrawn" Choosing Wisely. Sept 2013: July 2022:

forums.studentdoctor.net

What's your contralateral lung v5 on the rni plans?

 

[Palex80]

What's your contralateral lung v5 on the rni plans?

V5<60% for both lungs together, V5<70% as an acceptable deviation.

Constraints are for traditional fractionation (25 x 2 Gy)

 

[Ray D. Ayshun]

V5<60% for both lungs together, V5<70% as an acceptable deviation.

Constraints are for traditional fractionation (25 x 2 Gy)

You don't do a separate contralateral lung constraint? I think I do like 10-15% contralateral. Harder to get sometimes. Combined generally <50%. Though in line with separate discussion on lung coverage, looks like I'm cool with less coverage of imns than you. Depends on the situation though

 

[Palex80]

You don't do a separate contralateral lung constraint? I think I do like 10-15% contralateral. Harder to get sometimes. Combined generally <50%. Though in line with separate discussion on lung coverage, looks like I'm cool with less coverage of imns than you. Depends on the situation though

No, we don't use a contralateral constraint.

 

[Anthodite]

For comprehensive nodal irradiation:

For breast only:

For boosts:

For partial breast:

VMAT FOR...

Disclaimer: Posted already 2 years ago.

Breast IMRT Choosing Wisely... We Knew Ye

Pour one out for ASTRO's Breast IMRT Choosing Wisely. (Ed. note: Love the "recently published evidence" proviso and the past exonerative tense usage.) I believe this is the first ever "withdrawn" Choosing Wisely. Sept 2013: July 2022:

forums.studentdoctor.net

Omg I love visuals! Thank you so much for sharing those! I’ve never seen a VMAT breast dose distribution before so I wouldn’t have guessed the hotspots would look like that.

 

[Anthodite]

Not a loaded question at all. Google “twitter breast IMRT.”

IMRT is the standard of care for all early stage breast cancer whole breast RT (including two field tangent step and shoot with segments, and two field tangent inversely optimized sliding window IMRT) with proven less toxicity.*

*evidence based statement

WOAH I didn’t realize with how little I’ve seen it that was whole breast irradiation IMRT was one of THE standards for early breast cancers.

I think in terms of early stage/localized(I’m not sure but these are the patients that have a lumpectomy w/ clips which I think are T1/T2 N0M0) I’ve seen the IMRT all have been APBI or this one time of overlapping field was non-accelerated PBI.

If you don’t mind me asking: Would the difference between prescribing APBI and whole breast irradiation IMRT be if the patient had a lumpectomy as opposed to a mastectomy or are there other factors?

 

[TheWallnerus]

WOAH I didn’t realize with how little I’ve seen it that was whole breast irradiation IMRT was one of THE standards for early breast cancers.

I think in terms of early stage/localized(I’m not sure but these are the patients that have a lumpectomy w/ clips which I think are T1/T2 N0M0) I’ve seen the IMRT all have been APBI or this one time of overlapping field was non-accelerated PBI.

If you don’t mind me asking: Would the difference between prescribing APBI and whole breast irradiation IMRT be if the patient had a lumpectomy as opposed to a mastectomy or are there other factors?

Partial breast irradiation, versus whole breast, is recommended/standard for most women who get early stage breast cancer.

And IMRT is recommended/standard to deliver PBI, regardless of fractionation.

Put another way, whole breast RT and/or 3DCRT needlessly gives most women with breast cancer more toxicity versus PBI and/or IMRT.

(You can't really talk about PBI if there's a mastectomy.)

All the above are imho some of the most (if not the most) evidence-based rec's in all of rad onc, pound for data pound.

Partial Breast Irradiation Clinical Practice Guideline Replacement - American Society for Radiation Oncology (ASTRO) - American Society for Radiation Oncology (ASTRO)

View the updated PBI guideline based on a systematic evidence review

www.astro.org

 

[Anthodite]

I know this isn’t professional but OMG THANK YOU SO MUCH!! Literally was wondering this since I first learnt about treatment techniques in class! The differences for why a doctor my prescribe one technique over another were never covered in detail in my radiation therapy school classes besides the vague mentions&depictions of dose conformity. Thanks for explaining this in a level I can understand and taking the time to share those tables!!

 

[TheWallnerus]

I know this isn’t professional but OMG THANK YOU SO MUCH!! Literally was wondering this since I first learnt about treatment techniques in class! The differences for why a doctor my prescribe one technique over another were never covered in detail in my radiation therapy school classes besides the vague mentions&depictions of dose conformity. Thanks for explaining this in a level I can understand and taking the time to share those tables!!

As an epilogue will add that I think two-field tangent inverse optimized breast IMRT is the way to go, whether whole or partial breast, for most cases (as it will give less spillover into heart and lung). Many call this 3D or FiF etc, but it really is not and meets all requirements of the IMRT definition (fluences, modulation, inverse plan, etc.)

 

[Anthodite]

As an epilogue will add that I think two-field tangent inverse optimized breast IMRT is the way to go, whether whole or partial breast, for most cases (as it will give less spillover into heart and lung). Many call this 3D or FiF etc, but it really is not and meets all requirements of the IMRT definition (fluences, modulation, inverse plan, etc.)

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I vaguely recall dosimetrists tell me that the only difference between Field in Field 3DCRT and IMRT is that it’s done manually, but specifically that IMRT uses something called an “optimizer” to achieve the results.

Sorry for the late response I just took my radiation therapy boards(and somehow got registered as an RT(T) ). Thank you for showing me the info and especially where you got it from!!

 

[evilbooyaa]

I vaguely recall dosimetrists tell me that the only difference between Field in Field 3DCRT and IMRT is that it’s done manually, but specifically that IMRT uses something called an “optimizer” to achieve the results.

Sorry for the late response I just took my radiation therapy boards(and somehow got registered as an RT(T) ). Thank you for showing me the info and especially where you got it from!!

First off, congrats on passing. Appreciate your level of interest in the upper level things especially as a new grad.

There are multiple types of IMRT. WHat your dosimetrists have described to you is colloquially known as 'sliding window' IMRT, where the two tangent angles are fixed, but instead of 3 FiFs, there are 'infinite' FiFs, formed by a sliding motion of the MLCs. So the area being treated is the same as FiF,b ut potentially with better homogeneity (although a good FiF plan may reach something very similar to a sliding window IMRT).

There is then static IMRT, which is a multiple field plan (usually 3-5) that is similar to 3D-CRT but used intensity modulation to avoid OARs and improve homogeneity.

Then there is volumetric arc therapy (VMAT) which is IMRT with up to 360 beamlet angles (if doing a full arc) - a f ull arc would be surprising to see in breast since you don't need to have beams enter through the contralateral thorax.