Good News, But More Waiting
We got the results of the PET scan back.
We got mixed news so we're not really sure how to process it. It's not a mixture of good news and bad news. It's more a mixture of good news and uncertainty. And we feel a mixture of disappointment that it was not the ideal news we hoped for, but also optimism that it's still mostly good news and no obvious bad news. We don't feel like we can fully celebrate yet, but also don't feel like there's anything specific to lament either. We just have to keep waiting. Again. Waiting, waiting, and more waiting.
Here's the TL;DR:
The tumor itself has continued to shrink in size and, more importantly, the cell activity has decreased. The test showed that there is still activity in the area of the original tumor, which is pretty common for this type of lymphoma. Unfortunately, the activity is still at a level where it’s difficult to tell whether it’s just residual or unrelated activity, or if there are still cancer cells present. So I’ll have to have another scan in about 4-6 weeks to see if the activity has dropped to a level where they can confidently say that it is not from active cancer cells. Obviously, we would have preferred this to a be a slam-dunk showing no cell activity, but this is still mostly good news. It just means more waiting.
So, here's the more detailed version...
After another 5 days in the hospital this week, the kids were happy to have me home.
When it comes to lymphomas, doctors use PET scans to measure cell activity in the area of the tumor and then compare that to the activity of some consistent reference points (the liver and a blood pool found in the chest). This activity is determined by measuring the "uptake" - the amount of radioactive glucose absorbed by the cells (lymphomas like glucose, apparently). Once the uptake of the tumor area, the liver, and the blood pool are known, they then assign a score of between 1 and 5, where 1 is the best and 5 is the worst:
No uptake
Slight uptake, but below the blood pool
Uptake is higher than the blood pool, but below or equal to the uptake in the liver
Uptake slightly to moderately higher than liver
Markedly increased uptake or any new areas of concern
For lymphomas, you can consider there to be a "complete response" after treatment if the score is a 1 or 2 assuming everything else looks fine (no new tumors or areas of concern in the bone marrow, particularly). A score of 4 or 5 can be considered a partial response or poor response, depending on various factors and would likely require additional treatment, and at this point would also be considered bad for the overall prognosis.
I scored a 3. A score of 3 is a good response, and is often indicative of a complete response requiring no further treatment, but it has to be monitored to be sure.
So basically, a 1 or a 2 would have been great news. A 4 or 5 would be bad news. A 3 is good news, but we'll need to do some follow-up to make sure.
Studies have shown that for Primary Mediastinal B-Cell Lymphomas (PMBCLs), PET scans after treatment have really good negative predictive value, but not very good positive predictive value. That is to say, they're great at telling you if the cancer is gone, but not very good at saying with certainty that cancer is still there. With PMBCLs, it's typical for there to be a residual mass even after a completely successful treatment. So a residual mass is OK, as long as there is no activity within living cancerous cells.
More good news: I actually needed to shave for the first time in 4 months!
But even when you measure the activity (glucose uptake), things can still get a little muddy. Multiple studies have shown that there are numerous "false positives" when measuring the glucose uptake of PMBCLs after treatment. It's true that a Deauville score of 1 or 2 does seem to clearly indicate a complete metabolic response (i.e. there are no more visible living cancer cells). However, a score of 3 (or even 4 in some cases), while technically considered a "positive" indication that there is cancer present, frequently winds up being a false positive.
There is no definitive consensus on why this is. There are, however, two predominant ideas. The first is that one of the chemo drugs (rituximab) has a residual inflammatory affect that cause the surrounding area to "light up" on the scan. That "bright spot" of inflammation has a higher glucose uptake than the reference area, so it shows up as a false positive. The inflammation then subsides over time, leaving a clearer picture. The other theory is that it could be a thymic rebound. Apparently, the thymus can actually shrink during thymes (get it? haha...) of bodily stress. After the stress subsides, the thymus "rebounds" and grows back to normal size. Well, guess where the thymus is? Yup: smack dab in the mediastinum. So, again, this activity shows a higher glucose uptake, which then shows up as a false positive.
Edit: An oncologist friend emailed pointing out another possibility. He said that while different types of cancer grow at different rates, on average, it takes cancer cells 2 months to reproduce. So it could be that there are cells that are "lethally damaged", but haven't yet died. So repeating a scan a month or two later would show decreased activity as those cells die. So it may just be too early to tell if every last one has been killed.
Regardless of the reason, in multiple studies, PMBCL patients who have a post-treatment Deauville score of 3 have equally good outcomes as those with a Deauville score of 1 or 2. These studies all show that Deauville 1-3 have between 90 and 100% three- to five-year survival rates, depending on the study. And that's good, because for PMBCL patients, 18 months with complete response is considered likely to be cured.
In other news, youngest fell and got herself 3 stitches while I was in the hospital.
So where do we go from here? Basically, more waiting. I will have another PET scan in 4-6 weeks to see if the glucose uptake is subsiding, remaining the same, or increasing. We'll figure out where to go from there, but if that scan shows a continued reduction in activity that moves us to Deauville 2, then it will be considered a complete response and we'll move into follow-up with no further planned treatments. If things look about the same, we'll either continue to schedule PET scans or consider whether a biopsy is possible to see if any cancer cells are present.
Whew. Got all that? OK. So this is good news, but not slam-dunk, "we're done" good news. We've still got some waiting to do before we know if we're "in the clear". (Though, will we ever feel like we're "in the clear"?)
As we wait for the next scan, here's how you can pray:
Pray that the activity (glucose uptake) would sharply decrease by the next scan, thereby clearing up any confusion.
Praise that we seem to still be moving in the right direction, and maybe even close to a complete response.
Pray for our spirits as we continue our long season of waiting. We felt pretty disappointed that we didn't get the clear-cut, best news we were hoping for, but this is still good news. Yet, with each piece of good news, it feels like we still can't totally exhale because we're waiting on something else down the road.
After her stitches, baby girl surprised daddy with some unexpected snuggles.
P.S. Part of why it's taken a couple days to post this update, and why it may sound overly detailed and confusing, is because I didn't feel like I had a total grasp on what my scan result meant, and so I had to do some research. Science people, if you think I might have misinterpreted anything, please let me know. If you're curious, here are links to some of the studies I've referenced. (Sorry they're not properly formatted citations. We're trying to keep things somewhat informal here...) http://www.croh-online.com/article/S1040-8428(16)30244-X/fulltext#sec0120
