ctDNA Changes Early in Immunotherapy Predict Melanoma Outcomes
The potential to predict melanoma outcomes using circulating tumor DNA (ctDNA) levels shortly after starting immunotherapy is showing remarkable promise, according to a retrospective analysis presented this week. The study, published in JCO Precision Oncology, suggests that changes in ctDNA levels as early as 3 to 4 weeks into treatment can strongly indicate whether a patient will respond favorably, experience disease control, or face a higher risk of recurrence.
Researchers found that patients exhibiting a decrease in ctDNA levels from baseline had over 30 times the likelihood of achieving disease control, a 20-fold greater chance of an objective response, more than an 80% improvement in progression-free survival (PFS), and a 70% improvement in overall survival (OS) compared to those with increasing ctDNA levels. These findings could pave the way for earlier treatment adjustments and more personalized care for individuals with advanced melanoma.
Early Signals of Response
Immunotherapy, including checkpoint inhibitors targeting CTLA-4, PD-1, and LAG-3, has significantly improved survival rates for advanced melanoma. However, a substantial proportion of patients – estimated around 50% – do not benefit from these therapies. Determining which patients will respond remains a critical challenge.
Currently, clinicians typically wait 2 to 4 months to assess treatment response through imaging scans. This delay can be problematic, as apparent tumor progression on scans may sometimes be pseudo-progression – an inflammatory response mimicking actual growth – or simply normal inflammatory changes. CtDNA analysis offers a potential solution by providing an earlier signal of treatment efficacy.
“One of the challenges when treating patients with immune checkpoint inhibitor therapy is waiting anywhere from 2 to 4 months before we can actually get scans to assess treatment response,” explained Vincent T. Ma, MD, assistant professor in the division of hematology, medical oncology and palliative care at the University of Wisconsin Carbone Cancer Center. “Even then, we sometimes have difficulty interpreting it because occasionally we’ll see things that glance like progression, but could actually be just pseudo-progression, or just normal inflammatory changes in the tumors.”
How the Study Worked
The retrospective analysis, led by Dr. Ma and colleagues, involved 117 patients with unresectable stage III or IV melanoma who were receiving anti-PD-1 therapy. The primary endpoint was the association between changes in ctDNA levels and clinical outcomes. The study assessed baseline ctDNA levels and those measured 3 to 4 weeks after initiating immunotherapy.
The results revealed significant independent associations between both baseline and 3-4 week ctDNA levels and PFS and OS. However, the most striking correlations were observed with changes in ctDNA from baseline. Decreases in ctDNA were significantly linked to improved disease control, objective response rates, PFS, and OS.
Specifically, patients whose ctDNA levels decreased experienced a more than 30-fold increase in the likelihood of disease control (OR = 30.56; 95% CI, 10.64-87.74), a 23.5-fold greater odds of objective response (OR = 23.54; 95% CI, 8.58-64.57), and substantial improvements in PFS (HR = 0.18; 95% CI, 0.11-0.31) and OS (HR = 0.28; 95% CI, 0.13-0.56) compared to those with increasing ctDNA levels.
What the Numbers Tell Us
Patients with increasing ctDNA levels had a median PFS of just 2.3 months and a 12-month PFS rate of 23.1%. Their median OS was 14.1 months, with a 12-month OS rate of 43.5%. In stark contrast, patients with decreasing ctDNA levels demonstrated a 12-month PFS rate of 67.6% and a 12-month OS rate of 77.5%.
Further analysis showed that among patients with decreasing ctDNA, those who eventually achieved complete ctDNA clearance experienced even more significant improvements in PFS (HR = 0.14; 95% CI, 0.06-0.34) and OS (OR = 0.07; 95% CI, 0.02-0.27). The 12-month PFS rate for this group was 78.6% compared to 12.8% for those who did not achieve clearance, and the 12-month OS rate was 92.3% versus 40.5%.
Limitations and Future Directions
Dr. Ma acknowledged that the study’s retrospective design and relatively small sample size are limitations. “This was a small multi-institutional study, but we’re now in the phase of actually having more institutions participate so we can further validate these findings,” he said.
Another area for further research is determining optimal thresholds for defining significant ctDNA changes. The current study identified a 20% increase or decrease as potentially meaningful, but Dr. Ma emphasized the necessitate for more data to refine these cutoffs.
Practical challenges related to ctDNA testing, such as turnaround time and cost, also need to be addressed. Tumor-informed ctDNA platforms require initial analysis of tumor tissue to identify specific DNA alterations, which can delay testing. Current ctDNA testing isn’t always readily available or affordable.
“As of right now, you can’t obtain ctDNA results in real time,” Dr. Ma noted. “Perhaps one day we should be exploring ctDNA level changes as early as 1 to 2 weeks after starting immunotherapy.”
Implications for Patient Care
The findings suggest that ctDNA monitoring could enable clinicians to tailor treatment strategies more effectively. Patients with increasing ctDNA levels early in treatment might be considered for alternative therapies, such as BRAF-/MEK-targeted therapy or tumor-infiltrating lymphocyte (TIL) therapy.
“No longer are we thinking about just throwing the whole kitchen sink at patients,” Dr. Ma said. “We’re tailoring the treatment approach based on how well patients are doing early on, and thinking about this idea of personalized medicine during the actual course of therapy.”
Vincent T. Ma, MD, can be reached at [email protected].