Pet Ct Quesition

[boram]

Hi all

i want to ask what the success rate using Pet-CT-scan to detect cancer metastasis or cells on the lymph nodes ,how significant this test can be when considering RPLND procedure ?

boram

[Fed]

PET/CT has value in detecting seminoma relapses. It is far less reliable in the cases of non-seminoma. Although PET/CTs are sometimes ordered for non-seminomatous malignancies, the results cannot be deemed conclusive, hence the high reliance on CTs alone.

[Fed]

I also asked him about PET, since I came across a news release about a new Siemens HD-PET machine. He said PET scans have no advantage over CT's for TC mets, but he didn't explain why. Does anybody have good recent info to help clear this up?

Hi Paul,
For all germ cell tumors, a mass shown on a CT scan could be one of three things: active cancer, necrotic/scar tissue (post-chemo) or teratoma. Of these, only the active cancer will light up on a PET scan because teratoma usually resembles normal, homeostatic tissue. In the event of a possible seminoma relapse, the results are clear cut: a mass that lights up indicates a relapse, but a positive CT scan with an overlaying negative PET means scar tissue. In the case of non-seminoma, one cannot make a conclusive assessment because a positive CT scan with an overlaying negative PET can mean either necrotic tissue or teratoma, and the latter can only be treated by resection.
Hopefully this makes some sense. Let me know whether this helps in clearing things up.

[Fed]

For seminoma under surveillance, and without RT or chemo, there will be no scar tissue, so a CT alone should be adequate?

You are absolutely right.

You may also hear in subsequent posts that people may have random nodes showing up. For example, I have a 7 mm aortocaval node that has been stable since my first scan in February. My oncologist has said that as long as the nodes are < 1 cm and don't change shape, then there is no reason to worry about them.

[mercyriver]

I am going to go a bit off tangent from this thread.....is there a reason they would ever be concerned with a 7mm lymph node? I thought the normal size for a lymph node was 10mm. Or maybe I am a bit confused. Our oncologist always says it is hard to tell what size is "normal" for my husband, "because he is such a big guy". That is the reason they have always let his lymph nodes get over 20mm before they do anything about it. I also know that normal lymph nodes are not round they are more oval in shape and they become more concerning the more round they become.

Just wondering.....

Becki

[Fed]

I have never heard of lymph nodes greater than 1 cm being called "normal". In fact, even the NCCN guidelines note that stage N1 (clinical stage, assessed by CT) or pN1 (pathologic stage, assessed after resection) includes nodes that are less than 2 cm. Anything greater than 2 cm (but less than 5 cm) is already considered N2/pN2.

You are right about the shape, hence the comment on my previous post.

[veryworriedmom]

Paul

Fed explained it well. In my sons case, diagnosis seminoma stage 1 the CT scan did show an enlarged lymph but higher up, unusual for the typical progression, so they ordered a PET/CT and there was some increased glycolytic activity close to the surgical site. Could be reactive lymph due to surgery, could be something else, so they recommended close followup to see if any change in the next pet/ct in december along with monthly exam. In this case Pet/ct was helpful. In this diagnosis our insurance did cover it. Marion