Abstract 145P
Background
Assessment of molecular residual disease (MRD) by circulating tumor DNA (ctDNA) is a strong prognostic tool for post-surgery tumor recurrence for colorectal cancer (CRC), but it has been available only through clinical trials in Japan. Little is known about the clinical significance of ctDNA-based MRD testing for CRC patients (pts) ineligible for clinical trials due to age, comorbidity, etc. We have provided ctDNA MRD testing for CRC pts on a self-pay basis since June 2023.
Methods
CRC pts who received tumor-agnostic ctDNA MRD testing 4 to 8 weeks after curative-intent resection between June 2023 and March 2024 were prospectively enrolled and analyzed. When ctDNA MRD was present, follow-up imaging was performed to assess early recurrence.
Results
Among 32pts enrolled, 28 received ctDNA MRD testing 4-8 weeks after curative-intent resection. Median age (range) was 66 years (40-82), with 2, 6, 13 and 7 pts having pathological stage I, II, III and IV, respectively. Three of 7 stage IV pts received preoperative chemotherapy. Median turnaround time of the assay was 11 (6-13) days. Median follow-up time from surgery was 8 months. Post-surgery ctDNA was present in 7/28 pts (25%; 5 stage III and 2 stage IV), 5 of whom (71.4%) had metastases confirmed by imaging immediately following results (median 17 weeks after surgery). Median tumor fraction (TF) was 0.79% (range, 0.65-2.64) for pts with radiographic recurrence, which involved liver (3 pts), paraaortic lymph nodes (1 pt), and colon (1 pt). The 2 pts without recurrence had TF 0.11% (stage III) and 10.0% (stage IV) and received adjuvant chemotherapy. Among 21 pts without ctDNA MRD (stage I/II/III/IV: 2/5/8/6), no adjuvant therapy was provided for all stage I, II, and IV pts; capecitabine was prescribed for 5 of 8 stage III pts. No recurrences were detected in pts without ctDNA MRD as of moment.
Conclusions
For CRC pts undergoing curative-intent surgery, implementation of a tumor-agnostic ctDNA MRD test in clinical practice appears feasible, with comparable results to those of the clinical trials. This is the initial report on ctDNA MRD test for CRC in a real-world setting in Japan; follow-up is ongoing.
Legal entity responsible for the study
The authors.
Funding
Has not received any funding.
Disclosure
K. Kataoka: Financial Interests, Personal, Invited Speaker: Merck Biopharma, Eli Lilly. All other authors have declared no conflicts of interest.