A highly anticipated Phase III clinical trial has delivered mixed results in testing whether a blood-based test for minimal residual disease (MRD) could guide early treatment for colorectal cancer recurrence (CRC).
Published in Nature Medicine, the randomized double-blind ALTAIR trial tested whether trifluridine/tipiracil (FTD/TPI) could improve outcomes in patients with resected stage I–IV CRC who tested positive for Natera’s Signatera circulating tumor DNA (ctDNA) test after completing standard therapy but had no radiographic evidence of disease. However, the Phase III study—a collaboration between Natera and several Japanese research institutions and hospitals—failed to meet its primary endpoint for investigator-assessed disease-free survival (DFS).
The findings represent the first completed randomized Phase III “treat-on-molecular-recurrence” (TOMR) trial in CRC and underscore both the promise and limitations of ctDNA-guided intervention strategies, highlighting both the promise and limitations of precision oncology.
A slice of the GALAXY
In the ALTAIR trail, researchers from the National Cancer Center Hospital East in Kashiwa, Kansai Medical University in Osaka, and NHO Osaka National Hospital evaluated a small subset of patients from a larger clinical trial called the CIRCULATE-Japan GALAXY study. Between June 2020 and June 2023, the GALAXY study enrolled 5,514 patients with resectable stage 0–IV CRC across 152 centers in Japan and Taiwan. The GALAXY cohort and other datasets have consistently shown that postoperative ctDNA positivity is associated with markedly increased recurrence risk. ALTAIR addressed the next critical question: whether intervening at the point of molecular relapse alters clinical outcomes.
Among the 1,104 patients who tested positive for ctDNA following surgery in the GALAXY study, 243 were included in the ALTAIR trial, where they were randomly assigned to either six months of FTD/TPI or a placebo. With a median DFS of 9.3 months in the FTD/TPI arm compared to 5.5 months with a placebo, there was a 21% decrease in the risk of recurrence (HR 0.79; 95% CI 0.60–1.05). The difference did not, however, reach statistical significance (P=0.107).
Although the primary endpoint was formally negative, several exploratory analyses suggested biologic activity. Six-month DFS was 70.5% with FTD/TPI versus 45.5% with placebo, indicating an early separation of the survival curves. The benefit, however, decreased over time, with recurrence curves converging by around 24 months—a trend that aligns more with delayed recurrence than with the lasting elimination of residual disease.
The strongest signal emerged in patients with resected oligometastatic stage IV disease. In this subgroup, FTD/TPI reduced the risk of recurrence or death by 47% (HR 0.53; P=0.012). Investigators noted that stage IV patients also had the highest baseline ctDNA burden, suggesting that molecular tumor load may influence responsiveness to MRD-directed therapy.
A post hoc blinded central radiology review also shifted the primary analysis into nominal statistical significance. After adjudication of discordant imaging events, median DFS was 9.2 months with FTD/TPI versus 5.5 months with placebo (HR 0.75; P=0.0406). However, because the analysis was exploratory and non-prespecified, investigators emphasized that it does not alter the trial’s formally negative outcome.
The ctDNA dynamics themselves proved highly prognostic. Patients achieving sustained ctDNA clearance had dramatically superior outcomes compared with those with transient or persistent positivity. In patients with sustained clearance, median DFS was not reached, while it was 11.8 months for those with transient clearance and only 4.4 months for patients with persistently detectable ctDNA.
Notably, spontaneous or transient ctDNA clearance occurred in a subset of placebo-treated patients, highlighting an emerging challenge in MRD-directed oncology: distinguishing biologically meaningful ctDNA positivity from low-level fluctuation or transient shedding.
Tomorrow’s TOMR
The study also raises important questions regarding treatment intensity in asymptomatic patients with molecular relapse alone. Toxicity with FTD/TPI was substantial. Grade ≥3 adverse events occurred in 73% of treated patients versus 3.3% with placebo, driven primarily by hematologic toxicity. Severe neutropenia occurred in 56.6% of patients receiving FTD/TPI, and more than one-third required dose reductions. Despite these toxicities, no treatment-related deaths or new safety signals were observed.
The ALTAIR data arrive amid broader uncertainty regarding ctDNA-guided treatment escalation in CRC. The recent DYNAMIC-III trial similarly failed to demonstrate improved recurrence-free survival with ctDNA-guided intensification in stage III disease. Together, the studies suggest that while ctDNA robustly identifies high-risk patients, translating that prognostic information into effective therapeutic intervention remains challenging.
Still, the investigators argue that ALTAIR establishes the feasibility of large-scale MRD-directed trials and provides a framework for future studies using more active regimens, including immunotherapy combinations or anti-angiogenic strategies.
For now, the trial reinforces a central emerging reality in precision oncology: detecting molecular recurrence is increasingly possible. Preventing clinical relapse after detection remains the more difficult task.
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—its flagship benchtop sequencer—and AVITI24, which can simultaneously analyze DNA, RNA, proteins, and phosphorylated proteins.
