ctDNA accurate at diagnosing rectal cancer relapse
Combining circulating tumour DNA (ctDNA) with magnetic resonance imaging (MRI) can more accurately predict the likelihood of locally advanced rectal cancer (LARC) returning after treatment, Chinese scientists have found. In a new study published in PLOS Medicine, researchers describe how combining the techniques improved diagnosis and could improve treatment and outcomes for patients. In addition, the findings further strengthen the evidence for ctDNA as a biomarker for disease progression, say the authors.
Colorectal cancer patients given the all-clear after chemotherapy (nCRT) are subjected to a “watch and wait” strategy, involving regular MRI scans, to see if the disease returns. However, by using such an approach, there is a risk that cancer in such patients may go undiagnosed until it has reached an advanced – and, in some cases, untreatable – stage.
In fact, up to 25% of patients treated with chemotherapy will see their tumours return, in contrast to just 3% of patients who have undergone surgery. In each case, the earlier a tumour is diagnosed, the better the chances of a successful intervention.
Circulating tumour DNA has established potential as a cancer biomarker, but there are no current biomarkers for pathological complete response (pCR) or the absence of minimal residual disease (MRD) in LARC patients.
To fill the gap, a group of scientists in China studied 119 LARC patients undergoing chemotherapy for the condition. The team collected 531 serial plasma samples, before treatment, during treatment and after surgery.
“We found that baseline ctDNA features, as well as the clearance of ctDNA during nCRT, were significantly correlated with PCR status,” said the authors. Furthermore, the researchers discovered that combining ctDNA checks with MRI scans provide the most accurate results, enabling them to predict the likelihood of relapse. In addition, it helped identify those patients who could benefit from a watch and wait approach.
The findings provide a clear indication of the potential for ctDNA as a biomarker for LARC. However, the authors caution that “ctDNA clearance itself seems not to be a sufficient biomarker to predict recurrence.” The team are encouraged with the results of combining ctDNA screening with MRI scans and are calling for clinical trials to assess its efficacy.
They conclude that “ctDNA combining with MRI information achieved better prediction for nCRT response and has a potential to help patient selection in “W&W” strategy.”
At RGCC, we have pioneered a range of advanced tests that can detect and diagnose cancer, including ctDNA testing. Oncotrail RGCC provides clinicians with essential information on the presence of circulating tumour cells that can help identify both the type and concentration of cancer cells in a supplied sample.
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You can read the full paper, Utility of ctDNA in predicting response to neoadjuvant chemoradiotherapy and prognosis assessment in locally advanced rectal cancer: A prospective cohort study, here.