ctDNA Positivity Linked With Inferior DFS in Stage I to IV Colorectal Cancer

Longitudinal circulating tumor DNA (ctDNA) positivity detected at 4, 12, and 24 weeks after surgery in patients with stage I to IV colorectal cancer (CRC) was significantly associated with inferior disease-free survival (DFS), according to findings from the observational GALAXY trial (UMIN000039205) of the CIRCULATE-Japan project that were presented during the 2021 European Society for Medical Oncology World Congress on Gastrointestinal Cancer.

Results showed that the hazard ratio (HR) for DFS at the 4-, 12- and 24-week time points with longitudinal ctDNA positivity was 46.8 (95% CI, 11.1-197.0; P <.001); the sensitivity recurrence rate was 93.1%. At 6 months, the DFS rates were 99.7% (95% CI, 98.7%-99.9%) and 83.1% (95% CI, 75.0%-88.7%) for patients with ctDNA-negative and -positive disease, respectively.

Additionally, preoperative ctDNA was detected in 95% of patients with stage II disease (n = 267/280) and 96% with stage III CRC (n = 288/301). Although T stage was significant for preoperative ctDNA positivity, N stage was linked with postoperative ctDNA positivity at 4 weeks. No associations with RAS/BRAF V600E mutational status nor microsatellite instability (MSI) were observed.

“Further investigation [on] whether ctDNA status could become [a] new surrogate end point beyond DFS is warranted,” lead study author Hiromichi Shirasu, MD, of Shizuoka Cancer Center of Shizuoka, Japan, and coinvestigators stated in a virtual presentation during the meeting.

ctDNA can be used to predict recurrence risk through minimal residual disease (MRD) detection in patients with CRC. In the CIRCULATE-Japan program, investigators enrolled patients with resectable stage II to IV CRC to assess the utility of ctDNA analysis. The study is comprised of multiple parts: the observational GALAXY, the phase 3 VEGA, and the phase 3 ALTAIR trials.

In GALAXY, researchers utilized the Signatera bespoke multiplex-polymerase chain reaction next-generation sequencing assay, which was based on whole-exome sequencing of tumor tissue and matched normal samples. Plasma samples were collected prior to surgery and again at 4, 12, 24, 36, 48, 72, and 96 weeks following surgery. Investigators also assessed the link between perioperative ctDNA status and pathological stage (pStage), RAS/BRAF V600E and MSI status, and short-term outcomes.

A total of 1236 patients were enrolled between June 5, 2020, and February 28, 2021. Four hundred and twenty-eight patients were excluded from enrollment due to unavailable pStage from electronic data capture (n = 400), incomplete resection (n = 15), confirmed pStage 0 (n = 1), unavailable paired results of pre- and postoperative 4-week ctDNA (n = 6), and withdrawal of informed consent (n = 6). The final analysis included 808 patients with stage I to III colon cancer (n = 654) or stage IV CRC (n = 154).

The median follow-up was 5.5 months, and the data cutoff date was March 25, 2021; the test not performed rate using Signatera was 2.1%.

The success rates for ctDNA results before surgery, at 4 weeks, 12 weeks, and 24 weeks post resection were 99.0% (n = 799/807), 99.5% (n = 797/801), 99.6% (n = 531/533), and 100% (n = 263/263), respectively.

In the overall population (n = 808), 51% of patients were male and most (87%) had an ECOG performance status of 0. Patients had stage I (8%), II (35%), III (38%), or IV disease (19%). Half of patients were double wild-type for RAS/BRAF, 43% of patients had RAS-mutant disease, and 7% had BRAF V600E–mutant disease. Most patients (91%) had microsatellite stable (MSS) disease.

In the pStage I to III subset, the breakdown of tumor invasion was T1 (3%), T2 (12%), T3 (59%), and T4 (26%). Regarding lymph node metastasis, 54% of patients had N0 disease, 34% had N1 disease, and 12% had N2 disease.

Overall, the preoperative ctDNA detection rate was 92% (n = 734/799); these rates were 77% (n = 50/65), 95% (n = 267/280), 96% (n = 288/301), and 84% (n = 129/153) for patients with stage I, II, III, and IV disease, respectively. In the 4-week postoperative setting, these rates were 5% (n = 3/66), 5% (n = 15/278), 25% (n = 74/301), and 32% (n = 48/152), respectively; the overall ctDNA detection rate was 18%.

Further findings showed that 4-week postoperative ctDNA positivity was strongly associated with inferior DFS in the overall population (HR, 19.5; 95% CI, 7.9-47.8; P <.001) and in patients with pStage I to III disease (HR, 24.4; 95% CI, 6.9-86.5; P <.001). The sensitivity recurrence rates were 79.3% and 80.0%, respectively. In the overall population, the 6-month DFS rates were 99.0% (95% CI, 9 7.6%-99.6%) for ctDNA-negative patients and 80.4% (95% CI, 70.4%-87.3%) for those with ctDNA-positive disease. For those with pStage I to III disease, these rates were 99.2% (95% CI, 97.5%-99.8%) and 83.1% (95% CI, 69.9%-90.9%), respectively.

These data suggest that 4 weeks following surgery is a suitable time point for a ctDNA–based adjuvant trial, Shirasu noted in the presentation.

Multivariate analyses for ctDNA positivity were conducted both preoperatively and postoperatively. In the pStage I to III subset, covariates that were compared included T3 to T4 vs T1 to T2 (odds ratio [OR], 5.9; 95% CI, 3.0-11.9; P <.001), N1 to N2 vs N0 (OR, 1.5; 95% CI, 0.7-3.0; P = .31), RAS wild-type vs RAS mutant (OR, 1.8; 95% CI, 0.9-3.7; P = .12), BRAF wild-type vs BRAF mutant (OR, 2.9; 95% CI, 0.7-11.6; P = .14), and MSS vs MSI-high status (OR, 0.8; 95% CI, 0.2-2.9; P = .68). No significant differences with ctDNA positivity were observed with regard to sex or performance status.

In the postoperative 4-week multivariate analysis for ctDNA positivity, N1 to N2 disease vs N0 disease was the most significant factor (OR, 6.1; 95% CI, 3.5-10.8; P <.001). Additionally, the correlations were T3 to T4 vs T1 to T2 (OR, 1.6; 95% CI, 0.7-3.7; P = .29), RAS wild-type vs RAS mutant (OR, 0.7; 95% CI, 0.5-1.2; P = .22), BRAF wild-type vs BRAF mutant (OR, 1.1; 95% CI, 0.3-3.8; P = .86) and MSS vs MSI-high status (OR, 2.0; 95% CI, 0.6-6.4; P = .24).

Beyond known prognostic factors, multivariate analyses showed that ctDNA was the only significant factor for recurrence in patients with stage I to III disease (HR, 17.1; 95% CI, 4.6-63.1; P <.001). At the time of the presentation, no recurrences were reported in patients with T1 to T2 disease nor those with MSI-high status.

DFS was measured by preoperative ctDNA status in both subsets. In the overall population, the 6-month DFS rates were 98.4% (95% CI, 89.4%-99.8%) and 95.5% (95% CI, 93.1%-97.0%) for the ctDNA-negative and -positive patients, respectively (HR, 1.3; 95% CI, 0.3-5.3; P = .76). This was not a significant difference, Shirasu concluded.

Reference

1. Shirasu H, Taniguchi H, Watanabe J, et al. Monitoring molecular residual disease by circulating tumor DNA in resectable colorectal cancer: molecular subgroup analyses of a prospective observational study GALAXY in CIRCULATE-Japan. Ann Oncol. 2021;32(53):S222-S223. doi:10.1016/j.annonc.2021.05.015