im not a minimum dose guy
Where's the misunderstanding here? I don't care about hotspots in the implant. In simple terms, not asking the planning software to deliver prescription dose to 250 mls of silicone/saline would seemingly not change the coverage where it matters while delivering fewer mu's. Seems safer, kinda like treating bladder cancer with an empty bladder. Though I don't want to ruin your analogy, however irrelevant. This isn't about sparing the implant. Why target something with 0% chance of having cancer in it? And my dosimetrists won't mind as I actually draw out my own ctvs.Debating sparing a breast implant is the most RadOnc conversation I've ever heard.
How do y'all feel about bladder hot spots that are within the urine on planning?
None of the implant is the CTVTrue, the center of the implant is certainly not CTV.
Urine trouble nowDebating sparing a breast implant is the most RadOnc conversation I've ever heard.
How do y'all feel about bladder hot spots that are within the urine on planning?
From your paper: the dorsal part between the implant and the pectoral muscle/chest wall, containing eventual residual glandular tissue(Fig. 4C, blue contour): only to be included in case of thepresence of adverse tumour factors (Table 2).Was able to find way into ESTRO guidelines, and it looks like they exclude the implant in prepectoral positioning
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Post pectoral looks like a dream in that ribs etc get excluded by centimeters as has been said by Palex. A dosimetric paper was published in that context showing a not surprising decent reduction in ipsilateral heart and lung doses, though suprisingly, no difference in MUs despite a substantial reduction in PTV volume. In any case, I'll see how it looks in the prepectoral context.
right. My initial question was just wondering if people cropped out the implant, and if it was helpful. In my case, the plan is to treat the rind more or less, as they've outlined here. My guess would be that the implant is still getting reasonable dose globally. Just less. And in turn, the ipsilateral lung is getting less. Could be wrong. At the same time, if your coverage constraint is 95/95 when the implant is included, I suspect the implant can pretty easily be covered almost completely by prescription dose. In my case, the implant is 60% of the PTV. In turn to get to 95%, just 35 of the remaining 40% need be covered, which is to say, 87.5% of the volume that actually needs to be covered is being covered.From your paper: the dorsal part between the implant and the pectoral muscle/chest wall, containing eventual residual glandular tissue(Fig. 4C, blue contour): only to be included in case of thepresence of adverse tumour factors (Table 2).
No indications that you should avoid it with IMRT based mechanisms, unless I'm mistaken. Let me know.
People trot out boogey man arguments for “don’t do this” in rad onc a lot and I have been known to myself sometimes.The way optimizers plan these days you may full well avoid very high risk tissue by avoiding a giant blob of nothing in the middle. Are you guys avoiding contouring to the musculature for mastectomy patients (or giving full dose up to the musculature)? That is a bold move IMO, and not something I would want.
You are absolutely correct.None of the implant is the CTV
Not a single molecule of the implant will benefit from a picogray
though suprisingly, no difference in MUs despite a substantial reduction in PTV volume
Why target something with 0% chance of having cancer in it?
not asking the planning software to deliver prescription dose to 250 mls of silicone/saline would seemingly not change the coverage where it matters while delivering fewer mu's
Sure, agreed on translating volumes to MUs. I remain a little bothered by how much the machine sounds like a geiger counter at Chernobyl during SBRTs. That said, my surprise was based on the general appearance of the following plan from the publication. Just seems like the one on the left would be delivering fewer MUS.MUs are largely a function of segmentation and are normalized relative to a 10x10 open field. A CK plan targeting a tiny brain lesion may have an absurd number of MUs due to the dose being delivered through a tiny cone (that beam is on a long time). A heavily segmented plan targeting a smaller volume may require more MUs than a less segmented plan targeting a larger one.
It is not clear to me whether avoiding the implant or not is better for finding simple solutions to a breast plan that are delivering dose in a way that has been shown to work.
Lets say you include the implant in the CTV and have a 95/95 coverage criteria. There is expected build up under the skin surface and very simple solutions (tangents with a few segments) will get you coverage. Taking away the implant, you are now looking to get 95/95 to a thin slice of tissue between the implant and the body surface. This is going to require a more difficult solution and you may be driving to a plan that overdoses skin and subcutaneous tissue relative to standard.
For breast, I prefer simple solutions. For true IMRT breast, the issue is always the target volume. It might be appropriate to crop back a full 1 cm from the skin surface and RA everything (I suspect that we would have a hard time proving that this approach worse than any other strategy for breast cancer outcomes in the present environment of early stage diagnosis and good systemic therapy). This approach would of course give you a wonderful toxicity profile (although at times you will still be overdosing the heart relative to tangents). Now in this particular case, cropping back 1 cm from the skin surface would mean that you are only treating the implant!
No you won’t (especially in the case of inversely optimized two field opposed tangent IMRT), and I don’t think it will help much to carve, but I’d like to see.No one is arguing that the silicone or saline might harbor tumor cells and needs to be in the CTV. This is a dosimetry question. If you carve a hole in your whole breast target volume and try to use arcs with inverse planning with the implant goo as an avoidance structure you're gonna have a bad time.
The reason we don’t see MUs correlate with volume is due to the physics definition of a gray itself: joules per kilogram. As an extreme example, think of whole body 8 Gy wide open field and 8 Gy to a 10x10 open field… same MUs. There are simply more given photons in the former than the latter (because we relatively unimpeded their egress from the linac in the former versus the latter).That said, my surprise was based on the general appearance of the following plan from the publication. Just seems like the one on the left would be delivering fewer MUS
MUs are mostly a measure of beam on time, not dose delivered to target or integral dose. Beam on time correlates well with dose delivered in the unsegmented setting using the same open field, however, once you start modulating an open beam, the correlation is overwhelmed by other factors. A wedged plan alone will require more MUs to deliver the same dose to target.Just seems like the one on the left would be delivering fewer MUS.
Not sure about this...there is a correction for different field sizes. (a larger field does not actually need to be on quite as long to deliver dose to a certain point at depth due to contributions from that entire larger field... in other words, the output factor goes up). None of us do hand calcs anymore, but the newbies probably should know this for boards!As an extreme example, think of whole body 8 Gy wide open field and 8 Gy to a 10x10 open field
No you won’t (especially in the case of inversely optimized two field opposed tangent IMRT), and I don’t think it will help much to carve, but I’d like to see.
right. My initial question was just wondering if people cropped out the implant, and if it was helpful. In my case, the plan is to treat the rind more or less, as they've outlined here. My guess would be that the implant is still getting reasonable dose globally. Just less. And in turn, the ipsilateral lung is getting less. Could be wrong. At the same time, if your coverage constraint is 95/95 when the implant is included, I suspect the implant can pretty easily be covered almost completely by prescription dose. In my case, the implant is 60% of the PTV. In turn to get to 95%, just 35 of the remaining 40% need be covered, which is to say, 87.5% of the volume that actually needs to be covered is being covered.
Re subpectoral implants, these are target and OAR findings from paper I mentioned. Haven't seen anything published re prepectoral implants, which entails targeting a rind around the implant. EA = only targeting tissue anterior to the implantDo not include the implant in the CTV (as long as it's posterior to the muscle). As you have mentioned, do not constrain it, it's just not a target structure. Gets dose, doesn't get dose, whatever. Usually not an issue when people do 3D, but obviously matters w/ IMRT/VMAT.
MUs will be similar. Lung dose may be slightly better. Heart is unlikely to be significantly effected would be my overall guess.
I fully agree with the bolded. A smaller PTV is harder to meet 95/95 coverage on compared to a larger PTV (assuming the middle cavity is not an avoidance structure).
If one is painting the sea, one should use the color blue. If we analyze the average square surface area covered by blue in the sea paintings of Hokusai versus Monet, Hokusai uses significantly more blue. This proves Hokusai is better at painting the sea, and perhaps better at painting in general; more research is needed.Re subpectoral implants, these are target and OAR findings from paper I mentioned. Haven't seen anything published re prepectoral implants, which entails targeting a rind around the implant. EA = only targeting tissue anterior to the implant
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At this point, I'm just dragging things out for ****s and giggles as breast remains the worst. My original question can be rephrased now to: who is drawing the CTV on the left for PMRT in patients with immediate reconstruction and a prepectoral implant?If one is painting the sea, one should use the color blue. If we analyze the average square surface area covered by blue in the sea paintings of Hokusai versus Monet, Hokusai uses significantly more blue. This proves Hokusai is better at painting the sea, and perhaps better at painting in general; more research is needed.
waiting for the full publication before i apply.I didn't want to start yet another breast thread, but.....
How liberally are people applying B51 currently? Premenopausal? Triple Negative? "Multiple suspicious" (only one biopsied) LNs pre-chemo?
This isn't a great pre-publication B51 patient, right?
Walk through the logic of why not a great pre-pub B51 patient if you would be so kind, because else I’m making assumptions… like I assume if there were a publication the patient would be a great B51 patient??I didn't want to start yet another breast thread, but.....
How liberally are people applying B51 currently? Premenopausal? Triple Negative? "Multiple suspicious" (only one biopsied) LNs pre-chemo?
This isn't a great pre-publication B51 patient, right?
What sense does this make.waiting for the full publication before i apply.
I didn't mention, but she'd be mastectomy and I believe there was a "trend" toward improvement in mastectomy patients (would like to see data). 1 vs 3 enhancing nodes, primary size, primary response, etc... I don't think any of that specified in abstract. She's a very young patient and I'd rather err on the side of overtreating than undertreating. Particularly with incomplete information.Walk through the logic of why not a great pre-pub B51 patient if you would be so kind, because else I’m making assumptions… like I assume if there were a publication the patient would be a great B51 patient??
Our group has decided to wait for the publication before implementation in practice, though we do discuss with patients. More of to have something tangible to defend the decision of omitting RT. Wouldn’t expect stats to change but full details are nice to know. The whole change adoption curve in practice - our group is slow…What sense does this make.
Otoh. I saw people adopt MA20 and EORTC quite "liberally" (see below) just based on abstracts and presentations.Our group has decided to wait for the publication before implementation in practice, though we do discuss with patients. More of to have something tangible to defend the decision of omitting RT. Wouldn’t expect stats to change but full details are nice to know. The whole change adoption curve in practice - our group is slow…