Clinical implications of the ongoing GALAXY trial
Adjuvant (post-surgical) chemotherapy is useful in reducing the risk of disease recurrence and improving survival in patients who have undergone colorectal cancer (CRC) surgery. The GALAXY trial is evaluating the role for circulating tumour DNA (ctDNA) as a predictive biomarker to select patients with CRC who are most likely to benefit from adjuvant chemotherapy.
The GALAXY trial is prospective, observational study (one that follows the participants over an extended period to observe long-term outcomes) that monitors the ctDNA levels before and after surgery in patients with stage II-IV CRC to observe how they correspond to disease outcomes. ctDNA contains the DNA (genetic material) from cancerous cells and tumours and can be detected in the bloodstream. Depending on the levels of ctDNA in the blood, information on the tumour status such as whether it has responded to treatment can be gathered.
Early findings from the study demonstrate that there is a very minimal difference in disease-free survival (DFS) among patients who have ctDNA present in the blood and those that do not before surgery. ctDNA levels, however, do provide important prognostic insight after surgery, where patients who are ctDNA negative post-surgery experiencing better disease outcomes. While evidence does support that ctDNA status can provide valuable insight into which patients are more likely to experience disease recurrence or worse outcomes, it is still not clear if ctDNA status can help to guide clinicians and patients in selecting the best treatment options.
Ideally, ctDNA can be used in the future to help stratify patients who may only need a less-intensive post-surgical treatment compared to those who would benefit from more aggressive treatment. As such, patients can receive the most tailored and effective treatment with minimal toxicity and intervention.
Take away message:
The ongoing GALAXY trial aims to monitor circulating tumour DNA (ctDNA) levels before and after surgery in patients with stage II to IV colorectal cancer to understand how they correspond to disease outcomes. Early findings show that pre-surgical ctDNA levels do not provide important insight into disease-free survival, while post-surgical ctDNA levels are more strongly associated with the patient’s disease outcomes.
