drnick098

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I'm trying to decide on what to say for how to deliver ISRT for boards. Going through the articles/guidelines, ISRT is not well defined at all.

NCCN for HL:
"ISRT targets the site of the originally involved lymph node(s) and possible extranodal extension. The field encompasses the pre-chemotherapy and/or surgical volume, yet it spares adjacent uninvolved organs (such as lungs, bone, muscle, or kidney) when
lymphadenopathy regresses following chemotherapy."

So how much margin do you need to cover extranodal extension? This is very vague.

ILROG guidelines for HL by Specht, Yaholom et al PMID: 23790512

"Determination of clinical target volume
In principle, the CTV encompasses the original (before any intervention) GTV. Yet, normal structures such as lungs, kidneys, and muscles that were clearly uninvolved should be excluded from the CTV based on clinical judgment. In outlining the CTV, the following points should be considered:
Quality and accuracy of imaging
Concerns of changes in volume since imaging
Spread patterns of the disease
Potential subclinical involvement
Adjacent organs constraints"

This suggests that CTV = pre chemo GTV minus uninvolved surrounding normal tissue with whatever margin you feel like right? This is also very vague.

UK guidelines by Hoskin et al PMID: 22889569

"Gross Tumour and Clinical Target Volumes
Pre-chemotherapy imaging is used to define the superior and inferior extent of original disease, which is expanded cranio-caudally by a margin of 1.5 cm in the direction of potential lymphatic spread. This is slightly different to the involved-node radiotherapy volume, which has no expan- sion [20]. The margin has been introduced because currently most pre-chemotherapy PETeCT is not carried out in the radiotherapy treatment position and does not use the same immobilisation techniques (distinct from the recom- mendations in the EORTC-GELA Lymphoma Group paper [20]). The patient may change size and shape with tumour shrinkage after chemotherapy so the margin allows for both
positional and anatomical changes. There are also uncer- tainties in image registration to be accounted for as well the relatively low spatial resolution of PET imaging. It is not necessary to encompass entire nodal regions or adjacent areas. In the transverse plane, the GTV will include the involved nodes (or organ) only and any residual disease, not the whole pre-chemotherapy volume. The GTV should not extend into air, muscle planes or bone, unless the lymphoma is invading muscle or bone.
The CTV should be defined by hand as a direct three- dimensional volumetric expansion since using the treat- ment planning system expansion tool will overestimate the cranio-caudal extension and need to be extensively edited to constrain the volume within the nodal chain as well as air and tissue planes.
When pre-chemotherapy imaging is unavailable, the patient should be treated using involved-field radiotherapy."

This is the only guideline with a specific number for margins.

So what are you guys going to say for ISRT? A variable margin based on uncertainties on a per-patient basis and quantified as per your "intuition" as per ILROG guidelines? Simply use 1.5cm as per UK guidelines?
 

ramsesthenice

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I don't think there is but by definition there really can't be. Part of the purpose of ISRT is to reduce field size to exclude normal tissues as possible. I have seen Yaholom give a few presentations on this and based on the looks of everyones faces around the room I don't think that many people are really comfortable with the more extreme tissue sparing variants. Personally, I imaging this is a grey area and as long as you can justify what you are covering you should be fine. Unless there is a very good reason not to I don't think anyone would fault you proposing IFRT if you felt more comfortable, especially if that is how you practice at your institution.
 

Gfunk6

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I concur with ramsesthenice. For all ISRT plans, I draw out a GTV or, more precisely, a vGTV which I generally expand about 5 mm to create a CTV. The PTV expansion is highly variable and is dependent on the anatomic location, target movement, and the method of immobilization. It can range from as small as 3 mm (H&N) to as large as 10 mm (hilar mass w/ lots of movement on 4D CT).
 
OP
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drnick098

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Thanks for sharing your practice guys. I've also heard of people using 5cm expansions for "ISRT". That's really confusing. There's no good study to tell us what margins we should be using for "spread patterns" or "potential subclinical involvement" which ILROG advises should be taken into account. So it's anyone's guess right? The only published margin I can find is that 1.5cm margin recommended by Hoskin et al which isn't based on much but we can at least quote a paper about. The PTV margin is more easily justified. I'll probably stick to a 1.5cm cranio-caudal margin to CTV (and increase it as necessary if there are larger uncertainties) to be "conservative" and PTV as per anatomical location. No one has a strong argument against this approach?
 
Sep 18, 2013
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What do you guys think about ISRT for NHL? The NCCN guidelines recommend ISRT, but the ILROG guidelines were for HL. Is the safer way to go on the oral board exam IFRT for NHL and ISRT for HL?
 

medgator

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What do you guys think about ISRT for NHL? The NCCN guidelines recommend ISRT, but the ILROG guidelines were for HL. Is the safer way to go on the oral board exam IFRT for NHL and ISRT for HL?
Possibly. These guidelines are still very much a work in progress and you're correct about how that ilrog paper in the red journal only deals with hl.

Prepare to take heat from some of those lymphoma experts but technically, they can't fail you. How can they after all....the specific guidelines simply aren't there
 

Reaganite

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I stressed and stressed and stressed about this before boards last year. In the end, when I was asked about fields, I acknowledged that there was a shift away from IFRT with NCCN recommending ISRT, but that there were no consensus guidelines to define exactly what ISRT was. I explained to him I had heard Yahalom and others speak on this and it sounded like ISRT was essentially involved nodal with additional margins for target uncertainty (pre-chemo PET in different position than post-chemo CT sim, internal target motion, etc.), although again there were no strict guidelines. I said ISRT at my institution entailed fusing pre-chemo imaging to a planning CT, drawing a vGTV, and then putting up standard involved fields. We then modified the standard field--usually sup/inf--to avoid structures like the parotid, heart, etc. when the pre-chemo volume was clearly a good distance away from these structures. He asked me if that's what I did in my practice. I said "yes." We moved on, and I passed.
 

Palex80

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I have a problem with ISRT...

The guys from the UK brought out this wonderful paper describing ISRT, but has this concept ever been evaluated in any clinical trial? Nope...

INRT is being tested in numerous trials right now (for example in the German Hodgkins group trials) and was also evaluated in the British early stage trial too (RAPID).
However long term results from such reduced field techniques are lacking. I think we should be cautious.
 

Irradi8or

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What do you guys think about ISRT for NHL? The NCCN guidelines recommend ISRT, but the ILROG guidelines were for HL. Is the safer way to go on the oral board exam IFRT for NHL and ISRT for HL?
ILROG has written guidelines for ISRT for NHL as well, but not yet published. I've heard they should be coming out soon...
 

oldking

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Any additional thoughts on this topic, especially now that others may have started to prepare for oral boards since the original thread was started?

I am honestly very surprised that the NCCN guidelines for NHL specifically states to use ISRT rather than IFRT (it's not even listed as IFRT or ISRT, "ISRT (preferred)", or anything like that that gives one the option of IFRT) when the ISRT for NHL guidelines have not even been published (and forget tested in any study, as somebody notes above).
 
Sep 18, 2013
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It looks like the ILROG guidelines for NHL is available on the red journal website now...just in time for the boards. With NCCN and ILROG endorsing ISRT as standard for HL and NHL, I would assume it would be the same answer for the boards...thoughts? The interesting part is that even in the single modality setting with RT alone in low grade NHL, they recommend ISRT as well. Part of me wants to purge the traditional IFRT field borders from my memory but probably should resist that urge.

http://redjournal.org/article/S0360-3016(14)00064-9/fulltext