Heart dose in breast-RT

[Palex80]

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I have been reading the ASTRO guideline on breast cancer and they make the point that heart dose should be minimized by blocking it out of the tangent fields when treating the breast.
Interestingly a similar question was asked on the mednet and the posted reply also states the same.

It seems that people think we should do EVERYTHING possible to limit heart dose to 1-2 Gy.

I am not comfortable with that. I have several patients whose anatomy prohibits adequate coverage of the breast, if I was to totally block out the heart. We've tried prone and supine and even with DIBH it's not trivial to keep the heart completely out of the tangents, when you actually try to treat the entire breast.
The ASTRO guidelines makes the point that recurrence rates are still low when you block out the heart if the tumor wasn't situated in the blocked out part of the heart, but I am not aware of any good evidence to support this argument.

Our workaround is to use VMAT. You don't have the tangents going through the heart, yet there is still a considerable mean dose delivered by larger parts of the heart receiving (lower) doses. Our mean heart doses are usually around 2-4 Gy

How do you proceed here? Do you always block out the heart?

 

[medgator]

I thought the general goal was a mean heart dose of 3 Gy....

 

[nkmiami]

if the tumor is the upper quadrant, I was always block out that heart. I try to draw the LAD and make sure that it is safely under the block, since increased atherosclerosis/mi seems to be the primary significant late side effect. I dont think it is ok if the heart is getting a mean of 2 Gy and the LAD is getting 20.

Of course, this is for low risk disease. Good evidence for this is the recent european trial showing partial breast external radiation had equivalent results published in the Lancet last year.

Obviously, this is for low risk beast disease- Covering everything is more important when 10 nodes are involved,

 

[MDACCRules]

I have been reading the ASTRO guideline on breast cancer and they make the point that heart dose should be minimized by blocking it out of the tangent fields when treating the breast.
Interestingly a similar question was asked on the mednet and the posted reply also states the same.

It seems that people think we should do EVERYTHING possible to limit heart dose to 1-2 Gy.

I am not comfortable with that. I have several patients whose anatomy prohibits adequate coverage of the breast, if I was to totally block out the heart. We've tried prone and supine and even with DIBH it's not trivial to keep the heart completely out of the tangents, when you actually try to treat the entire breast.
The ASTRO guidelines makes the point that recurrence rates are still low when you block out the heart if the tumor wasn't situated in the blocked out part of the heart, but I am not aware of any good evidence to support this argument.

Our workaround is to use VMAT. You don't have the tangents going through the heart, yet there is still a considerable mean dose delivered by larger parts of the heart receiving (lower) doses. Our mean heart doses are usually around 2-4 Gy

How do you proceed here? Do you always block out the heart?

PBI is good evidence to support this. 90% of recurrences occur within a few cm of lump cavity. The only dose to the heart should be through scatter or transmission. No beams going through it. Despite the cautionary category, no study has shown an actual higher risk of recurrence in cautionary/unsuitable patients with PBI, and there are very large institutional studies (WBH, Tufts, combined analyses) that show no difference in breast recurrence (but unsuitable and cautionary had higher regional recurrence). So, if PBI works, the whole breast with heart block will work. BLOCK OUT THAT HEART.

MHD of 1-2 Gy should be easy when not treating nodes with a heart block, prone position, or DIBH if anatomy is a turd.

MHD of <4 Gy is attainable with DIBH almost all of the time. Also, there is no expectation to cover IMN with 95% to 95% (which is what the breast CTV should be covered with). It's a much lower coverage goal - i.e. in MA.20, they covered the vessels plus 1 cm with 80% IDL. With these techniques (heart blocks, DIBH, lower coverage expectations), it should be very rare to find someone that you can't minimize MHD to below 4 Gy (1-2% of patients). If you have trouble, i.e. are above 5 Gy, can consider raising the inferior border of IMNs (i.e. reduce CTV volume) or just explain that there is a increased risk of cardiac disease, but "you're 32 years old and have 12 positive nodes, so you probably need this treatment".

VMAT gives mucho integral dose and lung dose. Fair amount of studies showing this. There were reviews of community practitioners who thought this was a "better" approach, and were giving 8-9 Gy MHD.

There are many high quality discussions about this on TheMedNet. It's worthwhile to check there before asking internet yahoos.

 

[seper]

With VMAT, you'd have to presume 3-5% of scattered dose from the machine and the internal scatter components. Roughly 2 Gy goes to everything including the heart. I don't use VMAT for breast.

 

[medgator]

With VMAT, you'd have to presume 3-5% of scattered dose from the machine and the internal scatter components. Roughly 2 Gy goes to everything including the heart. I don't use VMAT for breast.

Yup, ditto with even standard imrt....heart inevitably ends up looking worse

 

[Reaganite]

Much to the chagrin of my associates and locums doctors I have been doing "most" of the breast for years and have never seen a recurrence. With the PBI/patterns of recurrence data and studies consistently linking heart dose to cardiac morbidity/mortality, I never felt guilty about it. I also frequently spare inframammary folds and axilla (usual areas of more aggressive skin reaction) in patients with high-lying or low-lying tumors respectively. Also have no problem cheating on medial or lateral coverage to ensure good coverage of lumpectomy cavity in patients with tumors that are far lateral and medial respectively. I know guys who will match electron beams to tangents in this scenario to cover every last inch of breast, which I always thought was overkill.

 

[OTN]

I also avoid IMRT and VMAT as much as possible in breast. Average heart dose is nearly always higher than I would prefer to see. Only use it when cardiac anatomy is such that a 3D plan would be terrible.

 

[nkmiami]

With VMAT, you'd have to presume 3-5% of scattered dose from the machine and the internal scatter components. Roughly 2 Gy goes to everything including the heart. I don't use VMAT for breast.

BTW: I dont use vmat, but i have seem some very good looking vmat plans in articles and at a demonstration. It really depends on contouring and planning. I do use imrt when treating imn/axilla/supraclav and find it helpful for sparing lung. Sometimes, have to avoid contouring breast tissue that is very close to the heart if the tumor is not in the medial inner quadrant. You can get very good plans with 3d/medial electron matches, but these have their own dosimetric issues, and signifcant acute skin toxicity.

 

[Gfunk6]

Palex, great post.

I have to admit that when I first joined practice I took the position that as long as NRG cardiac constraints were met, no further interventions were required. I've since come to believe that every cGy less you can deliver to the heart counts. As such we have made extensive use of DIBH for left-sided heart and, for lower risk women, will probably convert to IMRT-based APBI or, eventually SBRT.

We sometimes use VMAT for left sided cases when comprehensive regional coverage is needed. However, as pointed out by others, this really smears out the low-dose zone which can be counter-productive if you are trying to spare the heart.

 

[Gfunk6]

There are many high quality discussions about this on TheMedNet. It's worthwhile to check there before asking internet yahoos.

Yet your post was the most detailed and informative. MedNet is nice too, but just because some post has the picture/name of some new grad working in an academic satellite, it doesn't make it any more valid than what is posted on SDN.

 

[RickyScott]

Yet your post was the most detailed and informative. MedNet is nice too, but just because some post has the picture/name of some new grad working in an academic satellite, it doesn't make it any more valid than what is posted on SDN.

 

[Burt Radnolds]

I block the heart +5mm in most cases. See UK IMPORT LOW as well as other robust partial breast experiences mentioned above for proof of concept. Gets tricky sometimes when cavity is close. I almost never use VMAT or IMRT. I did just do VMAT for an inflammatory breast case with bad anatomy and got amazing lung V20 and mean heart dose compared to multiple other attempts, at the expense of horrendous lung V5 and V10. Given the diagnosis and the lack of clinic evidence that those constraints matter much, I was willing to accept it.

 

[nkmiami]

I block the heart +5mm in most cases. See UK IMPORT LOW as well as other robust partial breast experiences mentioned above for proof of concept. Gets tricky sometimes when cavity is close. I almost never use VMAT or IMRT. I did just do VMAT for an inflammatory breast case with bad anatomy and got amazing lung V20 and mean heart dose compared to multiple other attempts, at the expense of horrendous lung V5 and V10. Given the diagnosis and the lack of clinic evidence that those constraints matter much, I was willing to accept it.

Agree, there are extreme cases, where the heart dose is not much of a consideration, in fact, if the patient survived to experience a cardiac complication 20 years later, that may be an excellent outcome. Cant miss the forest for the trees.

 

[Palex80]

Thank you for all your posts.

Indeed the PBI-trial from the UK clearly points out that you can safely spare out parts of the breast without increase in recurrence rates, but these were not the patients I was referring to necessarily.
We deliver PBI whenever possible. I am also not adressing the patients who need RNI.

I am rather talking about the high-risk breast-only patients, that I wouldn't be so comfortable with to spare out parts of the breast by using blocks, even if the resection cavity is not near.
Patients who have a few of these risk factors: premenopausal, G3, LVSI +, multifocal, triple negative, lobular histology, extensive DCIS.

IMPORT LOW was great, but one needs to see which patients they included there. Most of them were low-risk.

The ASTRO guideline calls for mean heart doses <1Gy for right sided and <1-2Gy for left sided cases. That's tough to reach in quite a lot of patients without blocking out heart (and breast tissue) in my opinion.

 

[Burt Radnolds]

With my understanding of the data, if it were me, I'd take the heart block every time rather than passing direct beam or large amounts of imrt scatter through the heart.

Also, there are multiple data sets on apbi in high risk histology and they are fairly reasonable looking.

*Edit: There are definitely situations where you may need to exceed conservative heart constraints (multiple nodes, inflammatory), but for me almost none of those involve node negative T1-T2 patients.

 

[seper]

Breast patients with > 8 positive nodes are at very high risk of cancer-related death. Comprehensive irradiation improves survival. In these, heart dose is a secondary consideration.

 

[nkmiami]

I dont think the cardiac data shows excess deaths, just increased cardiac events, so lets not lose perspective here. There is data from denmark that there were excess cancer death for left sided vs right sided because they were not covering the imns on the left. Failure to cover the target is more likely to kill the patient than sparing the heart for aggressive cancers, but you should not have to choose as there are many techniques available.

DBCG-IMN: A Population-Based Cohort Study on the Effect of Internal Mammary Node Irradiation in Early Node-Positive Breast Cancer. - PubMed - NCBI

LAD MI is the source of most significant cardiac events from radiation and the lad can be against the chest wall. Mean dose to the heart is probably as meaningful as mean dose to the spinal cord, and just an indirect metric of dose to the coronaries for tangents, but not imrt. The title of NEJM article on this was "ischemic events"

 

[MDACCRules]

Look dude, you don't have to treat the whole breast. Those clinical/pathologic factors you mentioned have to do with overall recurrence risk, not risk outside of 2cm from the removed cancer. Hence, the minimal recurrence rate with PBI in "unsuitable and cautionary" patients. This is why people are saying not treating the whole breast is okay. Nobody is saying do APBI and treat the regional nodes (although, this is not irrational; it's just not standard).

If you want to lower the dose to the heart you have a few options: heart block, DIBH, prone technique, maybe VMAT/IMRT in a limited number of cases, and protons. The experts have answered - it's more important to lower heart dose than to treat 100% of the breast tissue. If you disagree, that's fine, it's a free-ish country. But, the data is strong enough to treat with a heart block. It's more cost effective to treat with heart block / DIBH compared to protons. Heart block / DIBH is dosimetrically better than VMAT/IMRT in the vast majority of cases.

Yes, you are correct - a heart block will block out breast tissue. However, that's not clinically relevant. Come on man. Let's just move on to regional Chinese food availability in small Midwestern towns. That's what this forum is BOUT

 

[HotSeat]

Without getting into specifics too much, I review cases of radiation failures, and have seen many marginal recurrences after whole breast radiation therapy for node negative patients, negative margins. There are a distribution of failures similar to the Emory paper (PMID: 23312271), which include breast parenchymal failures as well as failures in nodal regions that typically get diminishing doses with diminishing tangential breast field sizes. I don't know what the experts would say about this and don't care too much if they've already thrown the gauntlet down as the other poster said without addressing marginal failures, but I feel these are clinically relevant.

 

[Burt Radnolds]

Without getting into specifics too much, I review cases of radiation failures, and have seen many marginal recurrences after whole breast radiation therapy for node negative patients, negative margins. There are a distribution of failures similar to the Emory paper (PMID: 23312271), which include breast parenchymal failures as well as failures in nodal regions that typically get diminishing doses with diminishing tangential breast field sizes. I don't know what the experts would say about this and don't care too much if they've already thrown the gauntlet down as the other poster said without addressing marginal failures, but I feel these are clinically relevant.

I have seen many breast plans from other providers where the cavity itself is the only thing contoured and it's barely covered by the 90-95%, without margin. I am curious if these failures are mostly due to situations such as this. I always expand a cm, crop out of non breast tissue, and then expand by a PTV margin, much like you would construct an APBI external beam volume. This needs to be covered by at least 95% isodose line. I would not be surprised if some of these marginal failures were due to poor planning.

Also, ipsilateral breast failure is a well known event in whole breast radiation (14.3% at 20 years in B-06) and will inevitably occur no matter how well you plan.

 

[MDACCRules]

Without getting into specifics too much, I review cases of radiation failures, and have seen many marginal recurrences after whole breast radiation therapy for node negative patients, negative margins. There are a distribution of failures similar to the Emory paper (PMID: 23312271), which include breast parenchymal failures as well as failures in nodal regions that typically get diminishing doses with diminishing tangential breast field sizes. I don't know what the experts would say about this and don't care too much if they've already thrown the gauntlet down as the other poster said without addressing marginal failures, but I feel these are clinically relevant.

ARE YOU KIDDING ME? 12 out of the out of field recurrences (areas not getting 95%/95% are in the IM and SCV, and these are not parenchymal, so not the same issues as being discussed. 3 parenchymal failures were "in field" - i.e. within the 100% IDL, which means a heart block had nothing to do with it. 2 other parenchymal failures were in the so called "boost field" where the Rx was 15 Gy, but the delivered dose was 8.5 Gy, meaning there is someone who is not reviewing their plans. In the "marginal misses", 2 of the 9 were in parenchyma. They said they don't have an institutional policy of contouring nodal basins and that may have contributed to 5 of the marginal miss nodal recurrences. So, they don't do what evidence based breast radiation oncologists recommend, and they are surprised at the outcome?

Also, 791 patients and 35 had local recurrences, so about a 4% LRR, including nodal recurrences. It seems like if you make conservative estimate, if you treat every patient's whole breast without a heart block you may get down to a 3.6% rate. What a return!!

1. When you want to treat something, contour it out and target it with intention. 2. When you evaluate a plan, actually look at it, don't just take the dosimetrist's word for it. 3. Despite what you do, there will be "in field" failure.

Really not sure how this relates to not treating the whole breast. It sounds like a QC paper - poor technique and sloppiness.

 

[HotSeat]

The reason I brought up the Emory paper was because of the marginal miss in the whole breast case, not the other recurrences. They show a great example of where a recurrence can occur in a dose fall off region beneath the breast tissue in a whole breast patient. Marginal failures can be within the breast parenchyma in sub-whole breast treatments, or within the nodal regions around the breast that unintentionally get dose that may end up being helpful. If blocking of the heart results in blocking breast parenchyma or lower dose in these nodal regions, marginal recurrences could occur in those areas even with well planned sub-whole breast treatments. I feel these are clinically significant. I am most definitely not kidding you. I rarely post, but felt it was something to share from my own post-residency experience that will never be published, that marginal failures occur in whole breast radiotherapy, well-planned or not, which is what I see, and as fields get smaller for a larger number of patients, and heart blocking becomes more widely used, I expect to be reviewing more and more marginal failures. So I think the OP has a legitimate concern.

 

[evilbooyaa]

Hard constraint for us is mean heart < 4Gy for L-side. We usually achieve 1-3Gy. Certain extremely high-risk clinical scenarios can deviate from those guide lines.

I would wholeheartedly (almost) never do VMAT for breast. Tangential field in field IMRT (sliding window) should be fine, with SCV FiF or separate field boosting as necessary.

Recurrences happen, and it's a numbers game. I would not accept a mean heart >3Gy without some serious discussion with dosimetry. If the lumpectomy cavity is medial and inferior and patient can't do breath-hold and the mean gets up to 4Gy on that one patient out of 500, then that's OK as long as you think about it. Individual risk assessment for individual patients.

 

[scarbrtj]

Did someone already post this? Sorry, it's a bit TL;DR. Apologies if so.

Long-term heart-specific mortality among 347 476 breast cancer patients treated with radiotherapy or chemotherapy: a registry-based cohort study | European Heart Journal | Oxford Academic

 

[evilbooyaa]

Another group of people (the study above) that don't understand the point that is trying to be made. The risk is like 95% in left breast cancer patients undergiong radiation. If they're not left sided and not receiving RT then there isn't really a concern. The Darby paper is what I'd lean on.

 

[emt409]

Palex, great post.

I have to admit that when I first joined practice I took the position that as long as NRG cardiac constraints were met, no further interventions were required. I've since come to believe that every cGy less you can deliver to the heart counts. As such we have made extensive use of DIBH for left-sided heart and, for lower risk women, will probably convert to IMRT-based APBI or, eventually SBRT.

We sometimes use VMAT for left sided cases when comprehensive regional coverage is needed. However, as pointed out by others, this really smears out the low-dose zone which can be counter-productive if you are trying to spare the heart.

Funny you should mention, I am starting an SBRT for APBI candidates at our institution. We would eventually love to also do pre-NA chemoSBRT for high risk tumors too.

 

[evilbooyaa]

On protocol? What dose? I saw a poster that was 30Gy in 5 fractions using Cyberknife as APBI. Result: It's feasible with 12 month follow-up. My thought when I read it: No ****, sherlock.