PET Results

The PET scan was this morning.  While we were home, J seemed ready to cooperate.  One needle poke and he would be finished, then he would just need to lie on a table for 20 minutes.  Good plan until he had to drink nasty oral contrast material.  He decided he liked lemon flavor much better than raspberry flavor he was given.  He decided he needed to urgently go to the bathroom right before they were ready to inject him.  He decided (remembered, OK never really forgot) that he hates any sort of shot.  He told the family at dinner that he learned that even small needles hurt.  He finally was injected.  An hour later he was ready to be scanned, well kind of.  It took some convincing for him to allow us to position him on the table correctly.  The techs were patient and kind.


When we do a PET scan, we always perform it with something that lets us determine the density of what the radiation is traveling through.  Unless you are using a really old scanner, this is done by CT scan (some people call this a cat scan, but that gets confusing when you are also getting a pet scan), unless you have a really fancy PET scanner using MRI.  The CT scan was obtained first.

When the lymphoma was first diagnosed there were three large masses.  The largest mass was in the pelvis and was already turning to mush when we found it.  It was this mass that turned into the abscess between the 1st and 2nd round of chemotherapy.  The other two masses were next to the spine and right kidney in what we call the retroperitoneal space.  The two retroperitoneal masses were still present, but had considerably shrunk in size to where they are just a little bit bigger than normal lymph nodes usually can get.  The mass in the pelvis couldn't be seen anymore, but there was a little bit of soft tissue (as opposed to fluid or bone, most organs and masses are soft tissue density) that didn't belong in the pelvis.  Next to this was a small amount of fluid.  Both of these findings were right near the edge of where the original mass was, and they are at the spot where one of the drainage catheters was placed after the surgery to remove and drain the abscess.

The second part of the scan is the PET scan itself, showing where things are actively eating sugar.  The retroperitoneal lymph nodes had changed from being extremely active (consuming lots of sugar) to taking in no sugar (dead or treated lymphoma).  The fact that we could still see the lymph node on the CT scan doesn't bother me.  We see some leftover lymph nodes in a fair number of patients.  Those lymph nodes tend to get smaller and smaller over time, but may never completely go away.  So this was an excellent result.

The large pelvic mass is where things get a little interesting.   That small area of soft tissue had a little bit of activity.  It was enough that we can't just ignore it and pretend it isn't there. However, a radiologist that sees activity and automatically equates it with active cancer, is not being very thoughtful.  The degree of activity was similar to the level of activity found in the surgical scar in the abdominal wall.  Scar tissue and infection are things that can look like active cancer, because they also use sugar.  We are left with the dilemma of not knowing whether this is left-over scarring related to the infection and surgery that he had about 6 weeks ago, or if this is leftover active lymphoma.  It could possibly represent cancer cells that are resisting the chemotherapy and will come back with a vengeance in a week or so.

If there is any indication that this is active lymphoma, the plan would be to have more surgery to remove the mass and look at it under the microscope.  If there is active lymphoma, then he would get  two more cycles of chemotherapy (total of 6).  The surgery would need to happen before we started round 4 of chemotherapy.  Round 4 would then need to be pushed back for recovery time.  If they took it out and didn't find any significant amount of lymphoma, then he finishes after round 4 of chemotherapy, which would be delayed until he recovered from surgery.  One of the downsides of surgery is that they would be operating in a place where he has had an abscess and a prior mass.  Areas like that tend to get scarred down.  Surgeons operate through scars all the time, but the risks of complications from surgery around scar tissue increases.  It puts them at more risk of cutting something that shouldn't be cut.

If we really think this is just scar tissue, then we can proceed with chemotherapy as planned.  Because there is still a decent amount of activity, we would want to do another PET scan a few weeks after the 4th round just to make sure that it wasn't getting any worse, and that we weren't missing relapsing lymphoma.  We also would have the option of doing a scan right at the beginning of the 4th cycle to make sure there is not an enlarging mass in the pelvis.  If there were, we would return to the surgical plan.

It is my opinion that this represents reactive changes and that we would have to search hard to find active lymphoma.  One of the oncologists wandered into the radiology department as my colleague and one of the residents were reviewing the case, so I brought her to the reading room to see what her opinion was.  She liked my explanation as to why it was probably scar tissue and left over activity from the abscess.  She likes the idea of treating with round four, probably with an ultrasound at the beginning of treatment to see if a mass is suddenly growing.  Assuming there wasn't a mass, we would proceed with chemotherapy and get a PET scan a few weeks after chemotherapy, just to make sure we're not overlooking something.  She has two colleagues.  The three of them will talk it over and make a plan.  I hope they agree with me.  I would be happy to avoid another trip to the operating room.