Breast-RT and cardiac toxicity

[Palex80]

Hello!

I am wondering what kinds of contraints you use for breast RT when it comes to the heart.

Quantec does not offer lots of constraints, V25<10% is mentioned as one possible contraint.
http://www.ncbi.nlm.nih.gov/pubmed/20171522
This is generally well achievable with modern techniques.

Recently a EBCTG-analysis pointed out excessive risk for major heart events even with quite low mean doses of RT to the heart and without an apparent threshold.
http://www.ncbi.nlm.nih.gov/pubmed/23484825

I find it quite difficult to hold mean dose at very low levels (<5 Gy), especially with growing evidence for nodal RT and more patients receiving treatment to the axilla (and sometimes the IM).

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[hot sauce]

I try to stay within the NSABP B-51 constraints for all breast patients (I also use their contouring definition for the heart).

From the protocol:
whole breast only:
"≤ 5% of the whole heart should receive ≥ 20 Gy for left-sided breast cancers, and 0% of the heart should receive ≥ 20 Gy for right-sided breast cancers
− ≤ 30% of the whole heart should receive ≥ 10 Gy for left-sided breast cancers, and ≤ 10% of the heart should receive ≥ 10 Gy for right-sided breast cancers
− Mean heart dose should be ≤ 400 cGy"

Including complete lymph node coverage:
"≤ 5% of the whole heart should receive ≥ 25 Gy for left-sided breast cancers, and 0% of the heart should receive ≥ 25 Gy for right-sided breast cancers
− ≤ 30% of the whole heart should receive ≥ 15 Gy for left-sided breast cancers, and ≤ 10% of the heart should receive ≥ 15 Gy for right-sided breast cancers
− Mean heart dose should be ≤ 400 cGy"

 

[ShirleyT]

I have personally found it very difficult to actually treat the first three IM interspaces and achieve a mean heart dose under 4 Gy, even with IMRT, so will be interesting to see compliance with that trial, since IM coverage is mandatory if regional nodes are to be treated....... but maybe i am doing something wrong, so any feedback would be helpful.

 

[Irradi8or]

Even with breath hold?

 

[Palex80]

Thanks for adding the contraints, which are tough to meet if you are treating IM or sometimes even only the axilla (in my opinion).
I wonder where those contraints came out from. What NTCP-models are they based on?

Cardiac toxicity and associated dose constraints is something we know so little about...

 

[ShirleyT]

have not tried breath hold, maybe i should try breath hold with imrt when treating IMC nodes. Usually i had been reserving breath hold for tangents-only, but maybe it is time to expand my horizon......

i think the under 4 Gy mean dose came from the Darby paper, which has its problems as we have all discussed.

it is a bit reassuring that Lori Pierce did publish a paper showing no perfusion deficits at least at one year if mean heart dose is under 5 Gy, here is the pubmed link

http://www.ncbi.nlm.nih.gov/pubmed/23021709

 

[BobbyHeenan]

I am in agreement with comments above (re: <4-5 Gy mean heart dose being very difficult).

We use breath hold for left sided breast cancers when treating IM nodes (usually use a medial electron field(s) matched to tangent photons - see http://jco.ascopubs.org/content/27/31/e172.full.pdf).

Even with this technique, we often have trouble with mean heart dose <4 Gy, and sometimes <5 Gy is difficult as well. If we don't use the split electron technique then <4 Gy can be challenging.