Thanks for this link, it was very informative. Are you involved in research? I tried to sign up for the emails but it looks like you have to be a medical professional?
I may be wrong but I think the Tracc trial is observational to see if positive CTDNA has a bearing on recurrence? I don’t think there’s a placebo group as such? At my appointment today I was told it’s thought positive CT is an indicator of future recurrence and therefore it’s important those patients have chemo. With a negative result it is less likely to have a recurrence and Chemo may not be as important. However, It’s probably not that simple as Arial88 has found.
Hi, with Tracc you are randomised into either a test group or control group, the control group receives standard CAPOX. You are right, the trial is looking at possible overtreatment, so if you test negative for CT your chemo is de escalated, potentially just tablets not infusion, or even no chemo at all if Stage 2, which could be a huge win.
The slight issue is a delay ro starting treatment, plus if you subsequently test positive for CT after 3 months you then start 3 months of standard CAPOX, so longer on chemo. I was also high risk stage 3 so tempted to throw everything at it.
I was also worried if my result remained positive....... being a bit on the anxious side I wasn't sure how I wld deal with that.
But it's a fascinating development. Thanks for the link Hegsuk x
I have a science research background but not medical, I do read a lot of stats-heavy academic papers for work which made it easier but still a few things I didn't fully understand. I was able to read some of the references which were open.
Tracc has many parts, Tracc B was observational and has run since 2016 and the referred paper in that link gives the results. Tracc C (which I am on) is where they adjust treatment based on ctDNA, that only kicked off in 2022 a couple of months before I was diagnosed
Reading around a little, I think there is no single number for various reasons:
- There are multiple techniques for extracting the ctDNA which have different levels of error
- Each technique just gives an estimate of the amount of ctDNA in the sample. The decision on whether that is a "positive" is a human decision setting a limit balancing false positives and false negatives. But for each technique, there may be different limits for different medical situations, for example it's much more likely if you previously had a stage 3 cancer a low reading may indicate tumour but less likely for stage 1
- "Ground truth" is ambiguous. It depends on what time window you look at, how you try to detect it (MRI? Colonoscopy?) - for example there may be a small slow growing tumour that is not picked up in the time window of the study.
Having said that, for stage 2/3 colorectal it looks to be around 5-10% FPR from what I've read
