Great research from the journal Blood last week, an article called "Combined PET and ctDNA response as a predictor of POD24 for follicular lymphoma after first-line induction treatment."
Actually, two articles. The second is a commentary on the first, and might be even better, since it gets into why the first one is so important. The second is called "Cracking the POD24 code in follicular lymphoma."
As you can see from the two titles, this research focuses on POD24, or Progression of Disease within 24 months of receiving immunochemotherapy (like B-R or R-CHOP). When POD24 was first discovered, it was a big deal. There was finally a way to quantify a particular risk, and what that risk was. Basically, a patient labeled as POD24 received immunochemotherapy, responded to it, but had the disease come back within 24 months. (In the way it was originally formulated, POD24 doesn't apply to patients who had other treatments besides immunochemo, but I've seen it used for other treatments anyway.) This matters because POD24 patients have a statistically lower survival rate than the rest of the FL population. About 20% of FL patients are POD24.
The problem is, there is currently no reliable way to predict POD24. The work I wrote about recently on subtypes might prove useful some day, but for now, there's no way of knowing someone is POD24 until they receive treatment and the disease comes back. Lots of FL researchers say this should be a priority in the FL community (I tend to agree).
This research is an attempt to predict POD24 after the immunochemotherapy treatment.
As the chart in the second article shows, the tools we have now for predicting POD24 are pretty bad. They're very good at negative prediction, meaning they can tell us which patients are not POD24. But they are bad as positive prediction -- none of them are right more than 50% of the time. It's a flip of the coin. Or a FLIPI of the coin. (I hope at least one of you laughs at that, because it was an excellent joke.)
Two of the tools used to predict POD24 are PET scans and ctDNA MRD. We're probably all familiar with PET scans. They measure how much of a sugar solution is taken up by hungry cancer cells. If you're a patient with FL, you've probably had at least one.
ctDNA MRD means circulating tumor DNA Minimal Residual Disease. It measures the presence of cancer differently from a PET scan. Using some very sophisticated tools, the amount of cancer can be measured in the blood. It might be so tiny that a PET scan won't detect it. But if there is ctDNA still in the blood after treatment, it means the cancer was not completely taken care of.
As a predictor of POD24, a PET scan after initial treatment was able to predict POD24 about 45% of the time. ctDNA MRA was better -- it could predict POD24 about 58% of the time.
But the researchers in this article innovated by using both tools. When combined, they predicted POD24 about 85% of the time. Obviously, a huge improvement. And any improvement in predicting POD24 is great for new FL patients.
However, as that second article points out, the practical applications of this knowledge are a little complicated.
The problem comes from when the tests are given -- AFTER treatment.
If a clinical trial was conducted using this information, it would be run by first having a group of patients receive initial treatment -- let's say Bendamustine + Rituxan (to keep it as immunochemotherapy). If any patients were identified as POD24 with the PET + ctDNA tools, they could then be given a second treatment right away, something like CAR-T or a bispecific, both of which have been shown to work very well on relapsed or refractory FL. This could happen before the disease even came back officially (remember, it could take up to 2 years for the disease to show up again).
The problem is, it would be expensive and complicated to set up a clinical trial that gives that set up something as a comparison. In other words, it might be too complicated to show that the testing is better than what we have now.
Ideally, we'd have a biomarker that shows us POD24 BEFORE that initial treatment. To be clear -- this is a step forward. Anything that predicts POD24 accurately, even at this stage, is an excellent thing. Catching the cancer early might save a lot of lives.
It's another small step forward, and moving forward is what we want.
Stay well.