Webinar Session 3 – Q&A

How many years after radiation therapy does cardiac disease occur?

Conventional wisdom has been that it takes many years for cardiac injury to occur. However, there is increasing data to suggest that cardiac injury can occur sooner, perhaps within the first few years following radiation. We just published commentary on this exact topic in the red journal within the last month or two. That is easy to search under my name.  I will try to find the reference and post it.   In the Sarah Darby New England Journal paper she reported cardiac injury within the first year or two of radiation as well.

What is a typical/recommended translational threshold value in AlignRT for DIBH treatments?

We use 3mm. -Lily Tang

What tests should be included in SGRT commissioning per TG 147?

Hidden target end to end test, localization displacement accuracy and spatial reproducibility.

What mean heart dose do you try to achieve with various techniques used?

Our constraints for free breathing heart is 7Gy (8 Gy acceptable), DIBH is 6 and 7. –Lily Tang

Why IMRT and not 3D? What is the benefit of IMRT?

We do not recommend IMRT as a routine practice. We do it for double implanted patients with nodes. –Lily Tang

How do you reconcile the APBI data on local control vs. your data with cardiac block that indicates a possible increase in local failure?

APBI cases have been, I think, better selcted as “favorable’ cases.  the few cases of increased LF with heart blocks were in non-favorable patients (is my recollection).  Am I interpreting your question correctly??  thanks.  LMarks

With Vision RT how do you confirm, when re-acquiring reference images during treatment course, that the setup is accurate?

We capture a surface reference at the same time as taking the MV port film so we have confirmation that the setup is ok. -DGierga

If your patient is not positioned correctly does the system shine a light on the patient to let you know if you’re on or not? As you see it on the monitor.

It does not shine a light on patient, but it shows up on the screen, and it will automatically hold the beam. –Lily Tang

How many seconds is necessary the patient hold the breathing to be a candidate?

We can deliver the tx in pieces.  so this is not a huge problem.  Maybe 20 seconds is a reasonable minimum.  Essentially all healthy people can easily do DIBH.  -Lmarks

Assuming the operative bed is well covered by the technique used do you agree that it is acceptable to block the heart [in FB] to keep mean heart dose low [and hence under dose adjacent breast] and not use DIBH?  Many of such cases I have treated would have been candidates for APBI.

Yes. We often do NOT use DIBH if we can get an acceptable plan with FB scans.  You are correct that in many cases it is ok to not use DIBH, to block the heart completely, and accept the small area of skimpy dose in the inferior medial breast.  And yes, with DIBH, and less heart exposure, and the use of hypofractionation, the attraction of APBI is reduced.  -LMarks

You do CBCT or only port film?

We do MV port films only. other groups have published on cbct (see, for example, publications from the NKI). -David Gierga

What can you tell about the dose in the lung? Our experience shows it will be nearly the same, but its a interesting question. The density of the lung in DIBH should be smaller.

I believe the data show that the lung dvh values decrease since the lung volume increases with DIBH. -DGierga

If studies have shown that cardiac toxicities increases, should not all left sided breast patients be offered DIBH by default? What are you limitations for not doing this for all left sided breasts?

That is a logical approach. We have been doing this in a larger fraction of our patients as we are getting more comfortable with the approach.  The DIBH essentially will always result in less skimping on the medial inferior breast if you are intending to completely block the heart (which is usually my goal).   I do not do it in cases where I am comfortable skimping (older patients, tumors in the upper outer quadrant, etc).  So, in many cases if the tumor bed is far from the heart, you can treat with FB, block the heart, skimp a tad on the breast, and be OK.  It does add some conplexity that we do try to avoid if the patient does not need it. -LMarks

How do you set the zero/tattoo the patient? Free breathing or DIBH?

We tattoo patients in free breathing.

What kind of set-up images do you do? KV or MV?

MV.

Have you ever considered to do kv images insted MV images?

There is not much utility of seeing the clips on the kV image that is orthogonal to the beam path. So, in principle, you can see the clips on kV, it is easier to “know you are set up correct” by viewing the real portal image, and hence we make due with the MV image. Usually you can see plenty of anatomy on the MV port film to be comfortable that things are OK. -LMarks

Do you do daily images or weekly? What structures do you prioritize when you’re analyzing online images?

I think we do weekly imaging, maybe more at the start.  But the images usually align well.  I think we used to image more, but now are more confident with the surface alignment and are imaging less.   as a clinician, i look at the boney landmarks, the amount of lung and then try to assure that the heart is not in the primary beam (i usually try to totally exclude the heart from the beam). -LMarks

When you acquire 2 CTs (Free breathing vs DIBH) which one do you acquire first?

It does not matter. We do free breathing first. –Lily Tang

If using RPM where do you place the reflector marker?

If you were talking about CT SIM, you can place the marker wherever you get a decent external motion. –Lily Tang

How do you determine if the DIBH is reproducible during CT sim?

We have bellow to monitor patient’s breathing. You can use RPM as well. –Lily Tang

What are your mean times for CT acquisition and treatment (eg: 20min/fraction)??

CT times for CT planning are short; maybe 30 seconds.  For tx, we do not do CBCT.  The tx times are several minutes; maybe 8-10 min in room, and beam on time of a few min, maybe 2-3 min.  LMarks

Do you notice a difference between the first week of treatment vs weeks 2-4, for patient surface displacement due to tense muscles as the patient is nervous?

We have not seen this to be a problem. -D.Gierga

Has Inspiration hold technique been studied as useful for lung tumors? What are your thoughts Dr. Tang? Controls tumor motion?

Yes, we have treated lung DIBH as well. It is good for the tumor motion control. –Lily Tang

If you decide to TX a patient with DIBH who then needs an electron boost, do you use the DIBH or FB scan for boost?

We do it on FB for the boost.  We do plan off the DIBH scan, but use surface reference marks for the boost set up.   if we are concerned about this, we sued the FB scan. -LMarks

This is still very patient specific as body habitus and heat location and size are variables for left sided breast cases. What percentage of Left side breast patients in the study are viable candidates?

While there are some interpatient variations in anatomy, the DIBH will almost always reduce the amount of heart in the tangent fields. It is true that in larger women, the amount of lung and heart in the tangent fields is often lower than slim women, so the potential benefit is maybe less in very heavy women. Also, the very heavy patients are maube less able to do the DIBH, but i have not noted this to be a problem. I estimate that maybe 50-75% of patients with left sided cancer benefit. It all depends on how much you are willing to skimp on the left medial inferior breast coverage. when you block the heart you tend to skimp on that part of the breast, the degree of skimping is less with DIBH.  -Lmarks

You mention use of sticky bolus, would you be able to share manufacturer/name of that product?

Elasto-Gel. The item number for 0.5 cm is 486-970, you can easily find other thickness. –Lily Tang

Does the brass mesh bolus have any adverse effects on AlignRT imaging?

The speakers do not have experience with brass mesh bolus. If this bolus is reflective it might require some changes to be used with surface guidance.  I would recommend logging on to www.sgrt.org and check out the forums for an opportunity to ask this question, see pre-existing answers and go into more in-depth discussions as required.

How do you know if your port films were on inhale or exhale?  That would make a difference of the amount of the lung in the field.

We take them only in inhale. -LMarks

How do you deal with changes in breast swelling over the course of treatment when you use surface guided methods?

If the swelling is significant, you might want to re-take the reference. If it’s too much, re-scan is necessary. –Lily Tang

How do you modify your method for patients with bolus?

No, we just include the bolus into calculation. We use sticky bolus for DIBH treatment. It has a built in white fabric on one side. We do not SIM patients in bolus. It’s added during planning. You would need to acquire a AlignRT reference on day one. –Lily Tang

Clips can be visualised on kv images compared to mv images. Is there a reason why you do not use kv modality to visualise clips?

There is not much utility of seeing the clips on the kV image that is orthogonal to the beam path.  So, in principle, you can see the clips on kV, it is easier to “know you are set up correct” by viewing the real portal image, and hence we make due wotht he MV image.  Usually you can see plenty of anatomy on the MV port film to be comfortable that things are OK. -LMarks

Does VMAT have more “low dose spill” than fixed beam IMRT for DIBH Lt breast?

Yes –Lily Tang

Do your physicians have tolerances for the V5 lung dose when using VMAT or IMRT. Do you use VMAT / IMRT for IMN treatments not favorable for electron matching? Are you worried about flash with VMAT.

No, at this point, our main focus is on mean. DIBH would be 6Gy for ideal situation, and 7Gy is acceptable. FB is 7 and 8 Gy. –Lily Tang

What were the Netherland groups matching to on the CBCT?  Bone?  Soft Tissue?  Surgical Clips?

Unfortunately I don’t recall the details, but the two references that I mentioned are:
Betgen Radiother Oncol 106 (2013) p 225-230, Alderliesten IJROBP vol 85 No 2 p 536-542 2013
-DGierga

Do you use visual feedback for patients for the breath hold?  If so, goggles or ipad or other? TY

Vision RT has a visual patient feedback device, Real Time Coach, that can be used for DIBH. It is a small device that attaches to the treatment couch.

No CBCT even for VMAT Breast/Chestwall plans?

No. However, your physicians would need to make decision to either match the patient to bone or surface. –Lily Tang

Do you ever perform any CBCT’s on your breast patients?

No –Lily Tang

How quickly after surgery do you start RT? Do you see any reduction in swelling/patient contour?

Usually 4-5 weeks. If there is a lot of seroma or evolving scar, we would wait longer.  But usually by 4 weeks you are fine. -Lmarks

Do you ever have to change the thresholds during DIBH as patient relaxes?

Our routine practice is to use 3mm, and if patient cannot do 3mm, we will relax it till 5mm. If patient still cannot do it, we will treat patient in free breathing. We have experienced a couple of patients in 4 or 5 mm, and no one had to switch to free breathing. –Lily Tang

Do you always match MV EPI to rib cage and breast tissue or do you ever match to surgical clips?

Yes, to all of them.  and they should agree.  you do not always see the clips on MV images.  But, if you do, you can use that as a reference certainly. -LMarks

Can you obtain the CT data set for DIBH on an old CT that cannot do 4D CT?

You don’t need to do 4DCT. You just acquire a breath hold CT, and the CT skin rendering can be used as AlignRT reference. –Lily Tang

Have you been certified to use with Elekta Synergy?

AlignRT can be used with any linac to provide capabilities for accurate patient setup and monitoring of patient motion throughout treatment delivery in stand alone mode. The majority of linacs can also be directly interfaced to allow AlignRT to withhold beam delivery automatically when the patient moves out of position. These include:
Varian: CSeries and TrueBeam
Elekta: Versa HD, Synergy, Precis
Siemens: Artiste

At which point are the real time deltas calculated about?

RTDs are calculated relative to isocenter. The user does have the option to also look at the centroid of the ROI. -David Gierga

If you adjust the couch to meet the thresholds in DIBH how do you know the breathold is the same as planning CT?

If in doubt, please take a film. –Lily Tang