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SSO 2022 Press Release – Dynamics of Circulating Tumor DNA After Resection of Colorectal Cancer: GALAXY Study in Circulate-Japan

Global Header(Dallas – March 10, 2022, 4:51 p.m.) — A study presented at the Society of Surgical Oncology 2022 International Conference on Surgical Care has shown that patients with colorectal cancer can be stratified based on circulating tumor DNA status, with molecular residual disease positive patients potentially showing benefit from adjuvant chemotherapy across all stages.

Circulating tumor DNA-based molecular residual disease has the potential to identify patients who may benefit more from adjuvant chemotherapy by predicting recurrence risk and can evaluate the efficacy of ACT by monitoring MRD dynamics.

To examine this issue more closely, Eiji Oki, MD, PhD, FACS, from Kyushu University enrolled 1, 329 patients with State I-IV colorectal cancer between June 2020 and April 2021.

Dr. Oki and co-researchers used a personalized tumor-informed assay for the detection of ctDNA-based postsurgical molecular residual disease. Patients were then analyzed to determine six-month disease-free rates in excluding patients who enrolled phase III trials.

The analysis found that molecular residual disease positivity rate at 4 weeks was 16.4% (218/1,329) and was not different between laparoscopic and open surgery. However, patients with Clavien-Dindo Grade 2 or higher operative complication had a significantly higher positivity rate (9.6% vs 17.0%, p=0.002).

The six-month disease-free survival rate by ctDNA dynamics from 4w to 12w was 98% in ‘negative to negative’ group (N&#3f618), 62.5% in ‘negative to positive’ (N&#3f32), 100% in ‘positive to negative’ (N&#3f58), and 58.3% in ‘positive to positive’ (N&#3f78), with a significant difference between ‘positive to negative’ and ‘positive to positive’ groups with hazard ratio (HR) of 15.8 (95% CI: 5.7-44.2; p< 0.001).

Of 1,040 patients excluding patients who enrolled phase III trials, there were 183 patients with 4w-MRD+ and available molecular residual disease status at 12w; 96 patients received standard-of-care adjuvant chemotherapy by investigator’s decision. Cumulative incidence of ctDNA clearance was significantly higher in ACT vs. non-ACT (68% vs.10% at 24w; cumulative HR = 9.3; 95% CI: 4.6-18.9, p< 0.001). Among 4w-MRD+ patients, 6M-DFS rate was significantly higher in ACT vs. non-ACT; 84% vs. 34% (HR=0.15; 95% CI: 0.078-0.25; p< 0.001), which was observed in all stages, including pStage II.

“Our study demonstrated ctDNA dynamics during perioperative period and clearance associated with improved clinical outcomes in MRD+ patients. The study has shown that the patients can be stratified based on the ctDNA status, with MRD+ patients potentially showing benefit from ACT across all stages,” said Dr. Oki.

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