Webinar Session 2 – 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 proportion of your patients do you find DIBH is acceptable for?

Over time we have been using DIBH in more and more of our left sided cases. I would say that when become comfortable with the technique, well over half of the left sided cases are reasonable candidates. – Dr. Marks

We treat essentially all of our left sided breast cancer patients with DIBH. – David Gierga

More than 80% of our left-sided patients are qualified. – Lily Tang

How do you determine who is a good candidate? What are your criteria?

1. Patient needs to be fit and able to cooperate.   2. Anyone where the therapeutic ratio will be improved with DIBH.  this will include >50% of patients with left sided breast cancer.  And over time, we are using it in a larger and larger fraction of our left sided. patients.  It might be closer to 75% of the left sided cases.  We even use it now occassionally to reduce lung dose in right sided cases.

What heart dose objectives are you using for Lt Breast DIBH treatment planning?

I try to get the dose as low as I can.  In MOST cases, I choose to skimp on the coverage of the medial inferior breast in order to spare the heart.  So, unless there is a compelling reason to cover that part of the breast, I aim for a heart dose < 1 Gy.   I aim to get the heart out of the primary beam.  this is usually possible and oly skimps on a small part of the breast.  The essense of DIBH is that it reduces the amount of breast that you need to skimp on in order to fully block the heart.

How long after RT does it take for perfusion abnormality to manifest? Thank you

Usually within 6-12 months.   See IJROBP 2005, Marks et al

At MGH, do you use AlignRT at CT-Sim?

We currently do not. We mostly generate reference images directly using AlignRT at the time of the first treatment. Many groups also use a dicom based CT reference surface. -David Gierga

When the patient is on treatment, how do you adjust for the pitch when setting the patient up?

I like to immobilize patients in cradles during therapy to minimize these issues.  But i agree that localization errors can dwarf or negate some of the benefit of DIBH, so one needs to be careful about this. -LMarks

Do your therapists set up patients in the treatment room per AlignRT first before they exit the treatment room?

Yes.

How much physicist time is devoted to AlignRT?

It can be time intensive in the beginning, like any new technique, but once everything is up and running less time is needed. -David Gierga

What thresholds for the RTD do you use for rotation/pitch/roll?

3 degrees.

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.

How do you contour the heart?

There is an RTOG atlas I believe with guidance for this. I draw from the inferior aspect of the pulmonary arteries to the diaphragm, and cover all of the “heart” in that space, recognizing that some of it is really great vessels. I have started to more routinely draw the left main coronary artery if the field is close to the heart to be sure that I am off of that. The RTOG altas I think is publisehd in the Red J maybe 8 years ago?? -Lmarks

Would you recommend using FFF, to utilize a faster dose rate, so that the delivery will be faster, and the breath hold can be shorter?

I did not find it beneficial to use FFF on breast FFF. Patients can tolerate tangent or VMAT plans. I would avoid IMRT, because it usually end up with split fields, and then it will be more than 15 treatment fields–patient has to do more than 15 breath holds. In that case, patients cannot tolerate. –Lily Tang

Are port films also taken at breath hold? When a new reference image, do you take it simultaneously while taking the port films?

Yes, patients do breath hold for port films as well. We take a new reference image, and then use port film to confirm. –Lily

When using VMAT/IMRT what DVH goals do you use for planning (Heart, Left Lung, Total Lung)?

I try to get the heart dose as low as I can.  In MOST cases, I choose to skimp on the coverage of the medial inferior breast in order to spare the heart.  So, unless there is a compelling reason to cover that part of the breast, I aim for a heart dose < 1 Gy.   I aim to get the heart out of the primary beam.  this is usually possible and oly skimps on a small part of the breast.  The essense of DIBH is that it reduces the amount of breast that you need to skimp on in order to fully block the heart.

What is the recommended tolerance for RDEs?

I believe it’s RTDs, we use 3mm. -Lily Tang

How do you assess/quantify whether breath hold is reproducible?

We ask the patient to take several tests breaths at the time of CT sim to ensure reproducibility. Then at the machine we are monitoring with surface imaging.

Following up on quantifying reproducibility, how do you insure the amount of inhalation at CT is the same as the amount of inhalation during treatment?

We take an initial setup and breath hold image at treatment; also we look at the amount that the setup tattoo moves during DIBH at CT and can look at this at treatment as well. -David Gierga

Any comments on the repeatability of DIBH?

With proper immobilization, the reproducibility is about 2 mm. Here’s our publication:
6. X. Tang, T. Zagar, E. Bair, E.L. Jones, D. Fried, L. Zhang, G. Tracton, S. Xu, T. Leach, S. Chang, and L.B. Marks, Clinical experience with 3D surface matching-based Deep Inspiration Breath Hold (DIBH) for left-sided breast cancer radiotherapy, Practical Radiation Oncology, 2013, 4(3), pp.e151-8.
-Lily Tang

Do you have a heart constraint that is utilized to determine if you use the free breathing vs. DIBH for a particular patient? Or does the physician just eyeball it as implied in the talk?

I used DIBH whenever i can reduce the heart dose, which is in a large fraction of the left sided cases.  I try to get the heart outside of the primary beam.  That is usually a mean dose of < 1 Gy.  As a physician, yes, I eyeball whether or not to use the DIBH, but am using in in an increasing fraction of our patients.

Do you have any experience with replanning / resimulating due to changes in the patient anatomy (breast edema or shrinkage or change in weight)?

Yes we have experienced one patient that required re-scan. Her anatomy changed after the initial SIM. You do want to rescan and regenerate the AlignRT surface reference. –Lily Tang

You said you have reference surfaces you align to from both the free breathing scan and the breath hold scan.  Do you film both of these positions?  If not, how do you confirm the reference surface from the free breathing scan?  When you update reference surfaces, do you update both the free breathing and breath hold surface?

We only film the breath hold position, but we take a free breathing reference once the setup is confirmed. We feel its important to put the patient in a position to take a “good” breath. We’ll update both reference images if needed. -David Gierga

Why not using forward plan instead of VMAT?

I agree. I am reluctant to use VMAT for breast cancer.  We have been able to get very good dosimetry with partly wide tangents, with heart block, and DIBH.   So I worry that the lung and heart and contralateral breast doses are higher with VMAT.  whether this is clinically relevant is not known, but I worry.

What angles do you use for vmat?

60 ccw 301
300 cw 59
150 ccw 301
300 cw 149
– Lily Tang

For VMAT are you concerned with flash as well as V5 contralateral lung?

No, it’s a different planning than 3D tangent. We are not evaluating V5, but you can certainly do that. –Lily Tang

Do you think the VMAT plans provide better coverage than a field-in-field technique?

Yes, but we do not use it for all patients. Only for chest wall with reconstructions. –Lily Tang

Do you plan VMAT for breast DIBH technique?

Yes, we do it routinely. –Lily Tang

Do you have to use VMAT for DIBH treatment or can you treat patients with regular static tangent fields as well?

NO.  VMAT has absolutely nothing to do with DIBH.  these are separate issues.  Almost all of the DIBH cases we have done are with tangents and field in field technique.  -Lmarks

When and why do you need to “up-date” the reference images?

Occasionally we note discrepancies between port films and surface imaging. Since port films are still our gold standard we update the surface reference image(s) in these cases. -David Gierga

What was the name of the Swedish study for the placement of the device sternum vs abdomen?

The one that I quoted was actually from a Finnish group. Skytta Acta Oncologica 2016 Vol 55 No 8.

Do you treat the S/C in breathhold or free breathing?

We do now.  It took me a year or two to get comfortable with this.  I started using DIBH only in patients getting tangents only.  Over time, and encouraged by my younger colleagues, I got more comfortable with the matchline, etc, with DIBH.  You can do DIBH on the SC and tangent fields.

Question for the second speaker: how often do you have to adjust the ROI in the dry run for DIBH with vision RT?

Once the physicist gets used to select ROI, it does not really need to adjust the ROI often–will only for some very challenging patients. I would say less than 5%. –Lily Tang

Do you suggest video coaching during treatment? does Vision RT provide it in the package?

We have not used coaching recently.  I tried it early on and it was a a tad clunky.  Maybe the technology has gotten better.  we are able to get good clinical results with audio coaching.  I believe that Vision Rt does offer this option, but we have not used this most recent tool. -LMarks

Please comment on the use of visual coaching with DIBH, including quantitative improvement in reproducibility.

I have limited experience on visual coaching. It can improve reproducibility depends on the patients. Even without coaching, the reproducibility is about 2 mm–very good. — Lily Tang

How do you validate the Vision RT DIBH surface versus internal anatomy? MV ports only? KVKV? CBCT?

We use standard MV ports. Others have used CBCT to test internal vs external anatomy. -David Gierga

Patient education has been shown to be very important in compliance and anxiety, as noted by Dr. Tang.  Are there any recommended resources for patient videos, pamphlets, or, perhaps, scripting for patient ed?

We have print out, and also a video or actual tour for the patients would help. You want to ensure patients that they are not going to make mistakes. –Lily Tang

How long is treatment delivery using surface monitoring for DIBH tangents?

Once we got used to the technique there was no need to increase the treatment time slot. We treat our DIBH pts in a standard 12 minute time slot, with no additional time for surface monitoring. -David Gierga

What is the dose constraint for heat using VMAT or IMRT? Is it the same as normal 3D tangent tech?

For VMAT, the heart mean dose constrain is 8 Gy for left breast and IMN D95% >+ 90%. V25 Gy <= 25%. We would recommend avoid IMRT due to too many fields, which corresponding to the number of breath holds. For normal 3D tangent, V20Gy <=5%

Does the use of bolus affect the planning with DIBH?

Yes. We include the bolus in the dose calculation.

Are other institutions having issues with the use of bolus with AlignRT?

We were very worried about this at first and I was reluctant to use this approach in patients with bolus.  However, we got very careful with cutting the bolus carefully and placing it consistently on the skin (we mark the bolus; top, bottom, etc).  we now do use bolus and DIBH and are comfortable with it.   you might want to ask out therapists how they do it specifically. -LMarks

We have had success with bolus patients by covering the bolus with a thin sheet.

We use a special sticky bolus with one side is built in white fabric. –Lily Tang