ctDNA Negativity in Rectal Cancer Signals “Clear Stop” to Adjuvant Chemo

In a conversation with CancerNetwork^® at the 2026 ASCO Gastrointestinal Cancers Symposium, Nicholas Hornstein, MD, PhD, spoke about the clinical implications of updated results from the GALAXY study (UMIN000039205) assessing circulating tumor DNA (ctDNA) among patients undergoing upfront surgery for stage II to III rectal cancer. Findings published in Annals of Surgery showed that patients with ctDNA positivity experienced a significant disease-free survival benefit with adjuvant chemotherapy (HR, 0.28; 95% CI, 0.09-0.89; P = .031), while those with ctDNA negativity had no significant benefit (HR, 0.59; 95% CI, 0.26-1.35; P = .211).

Based on these findings, Hornstein stated that patients with ctDNA-negative status following resection may not need adjuvant chemotherapy. Although the GALAXY study was conducted in Japan, where practice for rectal cancer is “very different” compared with the US, Hornstein noted that it will be interesting to see how clinicians in the US incorporate these findings into their practice.

Hornstein is an assistant professor at the Donald and Barbara Zucker School of Medicine of Hofstra University and Northwell Health.

Transcript:

The GALAXY study was done in Japan. Practice is very different there for rectal cancer. In the United States, we do a lot of TNT: total neoadjuvant therapy. In Japan, they don’t. They go to curative intent resection for a huge number of patients, whether they’re node positive or not. If we want to extrapolate from the GALAXY setting to the US, there’s a few things that we can take away from it. The first is, potentially, patients in the adjuvant setting post-resection, if they’re ctDNA negative, don’t need chemotherapy; that’s a clear stop. How are we going to change our practice from TNT to other approaches? I don’t know if that’s going to happen. That ship might have sailed, but it’ll be interesting how we as a community embrace these new data and incorporate them into our practice.

Reference

Ando K, Hamabe A, Nakamura Y, et al. Molecular residual disease and recurrence in rectal cancer patients undergoing upfront surgery: a prospective cohort study. Ann Surg. 2026;283(1):13-21. doi:10.1097/SLA.0000000000006948