APPENDICURE

When you are living with appendix cancer or caring for someone who is, you quickly learn that one of the hardest questions is not just what treatment to do next, but who should even be considered for aggressive treatments like surgery.

Why ctDNA matters

A new study presented at the 2026 AACR meeting looks at something many of us have been watching closely: circulating tumor DNA, or ctDNA. This is the tiny amount of tumor DNA that can be detected in the blood. It is often described as a way to see cancer that scans cannot yet pick up.

This study focused on patients with peritoneal metastases from appendiceal or colorectal cancer who underwent surgery with curative intent. What they found adds an important layer to how we think about treatment decisions.

What happens when ctDNA is negative

First, ctDNA status before surgery mattered a lot. Patients who were ctDNA negative going into surgery had very strong outcomes. About 91 percent of those patients were alive at two years. That is a striking number in a group where outcomes are often uncertain. It suggests that when ctDNA is not detectable, the biology of the disease may be less aggressive, even if cancer is still visible on scans.

What happens after surgery

Second, even when surgery appeared successful, ctDNA often came back. Some patients who were ctDNA positive before surgery cleared it temporarily after surgery, but every one of those patients became positive again within six months. Among patients who started out ctDNA negative, about one third became positive after surgery, and most of those changes happened within the first year.

This tells us something important and difficult. Surgery alone is rarely eliminating all of the disease. There is often microscopic cancer left behind, and ctDNA is picking it up earlier than imaging can.

Rethinking where the cancer is

The most interesting and potentially practice changing part of the study has to do with where the cancer is located. Traditionally, patients with cancer confined to the peritoneum have been viewed differently from those with disease that has spread to multiple sites like the liver or lungs. Multi site disease has often been a reason to avoid surgery.

This study challenges that thinking. Patients who had multi site disease but were ctDNA negative still had strong survival, similar to patients whose cancer was limited to the peritoneum. In other words, the biology of the cancer, as reflected by ctDNA, may matter more than the number of places it has spread.

A shift toward biology driven decisions

That is a meaningful shift. It suggests that decisions about surgery should not rely only on what we see on scans, but also on what we learn from the blood.

The authors suggest that ctDNA could help guide several key decisions. It may help identify who is a good candidate for surgery, who is at high risk of recurrence, and who should be prioritized for clinical trials. It could also help shape how we use locoregional therapies in patients with more complex disease patterns.

The reality of recurrence

At the same time, the study reinforces a reality that many patients already know. Even after aggressive surgery done with curative intent, recurrence remains common. The rapid return of ctDNA in many patients highlights the need for better systemic treatments and more personalized post operative strategies.

What this means for patients and families

If ctDNA is negative, that is a very encouraging sign and may support moving forward with surgery even in situations that used to be considered too advanced.

If ctDNA is positive, it may indicate a higher risk of recurrence and a need to think carefully about additional or alternative strategies.

And perhaps most importantly, this study points toward a future where treatment decisions are based less on where the cancer is and more on how it behaves.

For those of us in the appendix cancer community, this is exactly the direction we have been hoping for.

You can read the original study here: Abstract 6444: Prognostic impact of ctDNA status and multi-site disease burden for patients with peritoneal metastases from appendiceal or colorectal cancer Free