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?
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?