Breast IORT further whole breast

[BobbyHeenan]

Quick question...

I have a patient treated with IORT at an outside institution for a stage I breast cancer and ended up having a positive node (1/3 SLN's, 3 mm of disease in the node, no ECE) and other risk factors (LVSI, margin < 1 mm).

There were recommended to have "25" more breast radiation treatments, but she lives closer to me so she wants it done here.

I'm seeing in the Targit trial they often did hypofrac whole breast, so not sure where the rec for 25 fractions is coming from.

I'm thinking "high tangent" 42.56/16....is there data that I need to be wary about this fraction size in this cohort? I'm not seeing any.

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[Gfunk6]

In the very beginning of our IORT program, we conventionally fractionated the whole breast if adverse pathologic features were found. This was done simply out of convention. However, it is now very clear via published data that it is completely safe to deliver hypofractionation after IORT so I agree that's what you should do. High tangents for a positive lymph node is also eminently reasonable.

 

[scarbrtj]

Quick question...

I have a patient treated with IORT at an outside institution for a stage I breast cancer and ended up having a positive node (1/3 SLN's, 3 mm of disease in the node, no ECE) and other risk factors (LVSI, margin < 1 mm).

There were recommended to have "25" more breast radiation treatments, but she lives closer to me so she wants it done here.

I'm seeing in the Targit trial they often did hypofrac whole breast, so not sure where the rec for 25 fractions is coming from.

I'm thinking "high tangent" 42.56/16....is there data that I need to be wary about this fraction size in this cohort? I'm not seeing any.

Prob a full boomer re: 25 fractions. One (provocative) read of the recent TARGIT is you gain ~0.5% of LC with EBRT but lose 0.5% in OS. (I said provocative!) Granted, it's a bit muddied as ~25% of the IORT patients did get EBRT. Re: high tangents, they register more on the nostrum vs effective side (for "favorable" SLN disease) in the many times which it's been analysed. As I recall even in Z0011 "a lot" (more than you'd think or hope) of patients got zero RT to breast or axilla; and with zero RT to breast or axilla, axillary recurrence was ~1%. IMHO you add beam here to up the in-breast LC (axillary nodes are a marker for breast recurrence, not axillary recurrence; and she had close margins, LVSI). Axillary RT just adds joules per kilograms of normal tissue without affecting natural history. To further add to my unorthodox take, I'd consider 42.4/16 instead of 42.56/16.

 

[kimplera]

d consider 42.4/16 instead of 42.56/16.

now there's a difference we should argue endlessly about

 

[scarbrtj]

now there's a difference we should argue endlessly about

Just to be clear I was being tongue-in-cleavage 'bout that. How do you divide 42.5 by 16? A machine that can give milliMUs? Still one of life's great mysteries.

 

[StIGMA]

Quick question...

I have a patient treated with IORT at an outside institution for a stage I breast cancer and ended up having a positive node (1/3 SLN's, 3 mm of disease in the node, no ECE) and other risk factors (LVSI, margin < 1 mm).

There were recommended to have "25" more breast radiation treatments, but she lives closer to me so she wants it done here.

I'm seeing in the Targit trial they often did hypofrac whole breast, so not sure where the rec for 25 fractions is coming from.

I'm thinking "high tangent" 42.56/16....is there data that I need to be wary about this fraction size in this cohort? I'm not seeing any.

My program treats the IORT component as the boost if there are adverse risk/post-op indications for whole breast radiation using the same fractionation as would have been planned upfront (almost always hypofrac). The breast does not like to slow cook.

 

[evilbooyaa]

Also had a boomer attending that was adamant about giving 50/25 in the post-IORT setting.

Used it as a 'weapon' to argue against IORT and try to 'push' people into 16 + 5.

Can you provide a link showing TARGIT-A used hypofrac for their WBI? There's too many publications off this one flawed study with hyperbolic conclusions.

 

[scarbrtj]

Also had a boomer attending that was adamant about giving 50/25 in the post-IORT setting.

Used it as a 'weapon' to argue against IORT and try to 'push' people into 16 + 5.

Can you provide a link showing TARGIT-A used hypofrac for their WBI? There's too many publications off this one flawed study with hyperbolic conclusions.

TARGITists said EBRT was between "3 and 6 weeks" in duration. There were Brits (inveterate hypofrackers) and Australians and French and even Americans in the study (tend not to be hypofrackers, but it varies as we know).

 

[BobbyHeenan]

Also had a boomer attending that was adamant about giving 50/25 in the post-IORT setting.

Used it as a 'weapon' to argue against IORT and try to 'push' people into 16 + 5.

Can you provide a link showing TARGIT-A used hypofrac for their WBI? There's too many publications off this one flawed study with hyperbolic conclusions.

Shoot - I had read it in commentary somewhere but like you're saying, in the primary source material I'm not finding an exact breakdown of EBRT dose schedules other than what scarb posted.

 

[Palex80]

Would any of you underdose the resection cavity bearing in mind that dose delivered with IORT was considerably higher than the normal "boost" dose we give after WBRT? I woulnd't advocate for it in this particular case given LVSI and close margins, but if everything was fine (small tumor, luminal A, wide margins) but WBRT was indicated due to considerable pN+. would you consider lowering the dose "a bit" in the resection cavity area?

 

[Gfunk6]

Would any of you underdose the resection cavity bearing in mind that dose delivered with IORT was considerably higher than the normal "boost" dose we give after WBRT? I woulnd't advocate for it in this particular case given LVSI and close margins, but if everything was fine (small tumor, luminal A, wide margins) but WBRT was indicated due to considerable pN+. would you consider lowering the dose "a bit" in the resection cavity area?

No, definitely would not. It's complex to do so and it may burn bridges in future if patient has local recurrence.