RCC resection bed recurrence

[Ray D. Ayshun]

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Discrete mass noted in resection bed ~2 years post nephrectomy. Biopsy proven recurrence. Not felt to be a surgical candidate, though I suppose some sort of IR-administered ablation is not off the table. Can RT be used? I can really only find studies done in the intact setting for gross disease.

 

[PhotonBomb]

This is gross disease. Small target.

SBRT all day. Cover as much of the tumor you can at 50/5, undercover the parts you need to for Bowel tolerances

Done.

 

[Pointless]

This is gross disease. Small target.

SBRT all day. Cover as much of the tumor you can at 50/5, undercover the parts you need to for Bowel tolerances

Done.

100% agree.

 

[Ray D. Ayshun]

This is gross disease. Small target.

SBRT all day. Cover as much of the tumor you can at 50/5, undercover the parts you need to for Bowel tolerances

Done.

Thanks. Belly board sim helpful here?

 

[Pointless]

Thanks. Belly board sim helpful here?

Wouldn't use a belly board here, just your standard SBRT setup... I find belly boards to introduce a level of inaccuracy that I wouldn't be comfortable with when using ablative doses. If the bowel ends up being that close, then I'd probably steer away from SBRT.

 

[Ray D. Ayshun]

Wouldn't use a belly board here, just your standard SBRT setup... I find belly boards to introduce a level of inaccuracy that I wouldn't be comfortable with when using ablative doses. If the bowel ends up being that close, then I'd probably steer away from SBRT.

Sure, but is conventional fractionation really worthwhile, or should I send them to ir?

 

[Pointless]

Sure, but is conventional fractionation really worthwhile, or should I send them to ir?

My experience is that if we can't ablate due to proximity to critical structures, IR will feel the same way. But yes, if you can't sbrt and they can ablate, then that's the way to go.

 

[xrthopeful]

if you feel like you can't do 5, then do 8 or 10 and respect timmerman bowel tolerances and you'll be A-OK

 

[Burt Radnolds]

If the a/b of the tumor is lower than that of the OAR, as it very well may be in this case given the RCC and delayed recurrence, then SBRT should work in your favor and I would just get in what you can with 5 fractions

 

[RickyScott]

if you feel like you can't do 5, then do 8 or 10 and respect timmerman bowel tolerances and you'll be A-OK

Agree with this- try to get bed above 100. In abdomen may consider Chris crane fractionations 67.5/15 75/25, even if can’t cover entire ptv: use his tolerances and expansions.

 

[scarbrtj]

If the a/b of the tumor is lower than that of the OAR, as it very well may be in this case given the RCC and delayed recurrence, then SBRT should work in your favor and I would just get in what you can with 5 fractions

An interesting situation arises when α/βtumor<α/βlatenormal. If I could still solve partial first order differential equations, I could prove it to you. But by brute force (fortunately you only have to look at 1, 2, 3, 4, or 5 fractions) you can show that a single large fraction is the best option when trying to maximize tumor effect without increasing (i.e. constrained by) late side effect. For example, say a tissue late tolerance is 54 Gy/27 fx, BED Gy3=90 (α/βnormal= 3), and the RCC α/βtumor =1.5 (BEDGy1.5 thus equals tumor effect BED). Keeping late effects the same, if you give:

One fraction of 15 Gy, BED Gy3=90 and BED Gy1.5=165.
Two fractions of 10.2 Gy, BED Gy3=90 and BED Gy1.5=159.
Three fractions of 8.1 Gy, BED Gy3=90 and BED Gy1.5=155...

and so on and so forth. The one fraction regimen thus has the equivalent late effect profile, superior acute effect profile (a very superior BEDGy10 profile because its total dose so low) and superior tumor effect profile versus any other multi-fraction regimen conceivable. So why isn't the single fraction regimen used in situations (e.g. prostate?) where we truly think α/βtumor<α/βnormal? E.g., if one truly thinks this, and one has radiobiology knowledge, one would use one fraction instead of five. (Has been tried in prostate; OK outcomes except maybe in tumors that really weren't α/βtumor<α/βnormal.) Just a pleasant Sunday morning thought.

 

[Ray D. Ayshun]

An interesting situation arises when α/βtumor<α/βlatenormal. If I could still solve partial first order differential equations, I could prove it to you. But by brute force (fortunately you only have to look at 1, 2, 3, 4, or 5 fractions) you can show that a single large fraction is the best option when trying to maximize tumor effect without increasing (i.e. constrained by) late side effect. For example, say a tissue late tolerance is 54 Gy/27 fx, BED Gy3=90 (α/βnormal= 3), and the RCC α/βtumor =1.5 (BEDGy1.5 thus equals tumor effect BED). Keeping late effects the same, if you give:

One fraction of 15 Gy, BED Gy3=90 and BED Gy1.5=165.
Two fractions of 10.2 Gy, BED Gy3=90 and BED Gy1.5=159.
Three fractions of 8.1 Gy, BED Gy3=90 and BED Gy1.5=155...

and so on and so forth. The one fraction regimen thus has the equivalent late effect profile, superior acute effect profile (a very superior BEDGy10 profile because its total dose so low) and superior tumor effect profile versus any other multi-fraction regimen conceivable. So why isn't the single fraction regimen used in situations (e.g. prostate?) where we truly think α/βtumor<α/βnormal? E.g., if one truly thinks this, and one has radiobiology knowledge, one would use one fraction instead of five. (Has been tried in prostate; OK outcomes except maybe in tumors that really weren't α/βtumor<α/βnormal.) Just a pleasant Sunday morning thought.

Fwiw, a number of retrospective studies have employed 25-26 gy x 1 for intact rcc, with the advantage of having normal kidney around to serve as spaceoar.

 

[taserlaser]

Fwiw, a number of retrospective studies have employed 25-26 gy x 1 for intact rcc, with the advantage of having normal kidney around to serve as spaceoar.

Just did one of those last week in fact. Works well.