Gastric lymphomas

[ShirleyT]

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Question for fellow rad onc folks:

What margins are you using to around the stomach to create the PTV for gastric malt lymphoma?

Thanks!

 

[Gfunk6]

It depends on what you are using for IGRT. However, given the very low doses involved I think 0.5 cm with daily volumetric imaging would be reasonable. If you are using EPID (2D) then bumping it to 1 cm would be a good idea.

 

[G'ville Nole]

I agree with the above expansions. I'll add the caveat that I try to do these patients 1st thing in the morning with instructions to fast after midnight. Differential stomach filling will easily plow through any reasonable PTV expansion you use, so I bring 'em in empty and hungry.

 

[seper]

Slightly off topic.
What's the appropriate field arrangement? Classic AP/PA would never result in acceptable heart dose by current standards. What would you say on oral boards?

 

[deleted4401]

Isn't it only 30 Gy/20 fractions?

 

[ShirleyT]

Thanks so much for all of the helpful responses! I am going to have my patient NPO past midnight, do a 4DCT sim to account for resp motion, then add a 5 mm PTV and go with daily cone beam CT for IGRT. I am going to do IMRT to spare the heart and kidneys as much as possible

I was planning on 30 Gy in 20 fractions, based on the paper in JCO from MSKCC which showed very good local control (this patient has low grade gastric malt lymphoma).

 

[medgator]

Slightly off topic.
What's the appropriate field arrangement? Classic AP/PA would never result in acceptable heart dose by current standards. What would you say on oral boards?

Either a 3-field or 4-field arrangement should work. I don't think IMRT is necessary most of the time, although you could probably justify it being so close to the kidneys.

this might be helpful:

http://www.ncbi.nlm.nih.gov/pubmed/15936555

Where I trained, we used to do 30 Gy/17 Fx, but anecdotally, giving it in 20 Fx (1.5 Gy/day) may help to reduce side effects.

 

[ShirleyT]

Either a 3-field or 4-field arrangement should work. I don't think IMRT is necessary most of the time, although you could probably justify it being so close to the kidneys.

this might be helpful:

http://www.ncbi.nlm.nih.gov/pubmed/15936555

Where I trained, we used to do 30 Gy/17 Fx, but anecdotally, giving it in 20 Fx (1.5 Gy/day) may help to reduce side effects.

Thanks for the link!! that was a good paper. Interesting, that paper from MSKCC they used a 2 cm PTV!! that seems HUGE and would be overlapping into heart and kidneys!! I wonder why they used such a big PTV?

 

[bobloblaw]

I recently treated a patient with a gastric lymphoma, she was elderly and a little frail so I used 30 Gy in 20 fractions and she did not throw up on the table. or me. (anecdotal success!).

I used kV cone beam CT for imaging and had the patient come in with an empty stomach for simulation and then NPO every day for treatment.

Even with kv cone beam, it was harder to visualize the stomach than I expected. There were air bubbles in the adjacent loops of transverse and descending colon that pushed the stomach around to different degrees day to day. The therapists naturally wanted to line up to bony anatomy so it was really important to make sure that the fields were lined up to the stomach.

even with the patient NPO, there was a lot of variability in the position and shape of the stomach so I think a 5 mm PTV expansion could be very tight. I ended up with a 1.5 - 2 cm block margin (including the CTV and PTV margins) but was tighter near the heart and kidneys. The larger margins helped because the "shape" of the stomach changed a little from day to day (even when the patient was consistently NPO).

I used a 3D plan (4 fields including obliques) and the liver, lung, kidneys and heart were fine - but it depends on your patient's anatomy and the dose constraints you want to shoot for.

I'd be careful about using small or tight planning margins - the dose is only 30 Gy and it would be really painful to have a marginal miss when radiation is the curative modality.