Background: Non-invasive methods to monitor for colorectal cancer (CRC) recurrence suffer from lack of sensitivity (e.g. CEA) or radiation exposure (e.g. CT). We have previously described a blood test for CRC based on detection of two methylated genes that may indicate invasive tumour DNA shedding into the blood (1).
Aim: To present initial findings correlating methylated biomarkers with CEA and recurrence uncovered by radiological follow up.
Methods: Methylated BCAT1 and IKZF1 DNA and CEA were measured in patients previously diagnosed with CRC. Blood was collected before or after intervention including surgery or chemo/radiotherapy. Records for those patients positive for either test were reviewed to determine if a recurrence had occurred.
Results: Following treatment, patients who were methylation test positive prior to treatment showed no methylation (22/30, 73%) or significantly reduced methylation (6/30, 20%) a median 3.8 months after treatment. Records for 89 post-intervention patients who had both tests a median 10.6 months after treatment were reviewed. One patient positive for both tests was shown to have liver metastasis. 65 (73%) were negative for both assays and 23 (26%) patients were positive for the 2-gene blood test but negative for CEA. Records for the latter patients identified 6 (26%) with local or distant recurrence, 6 (26%) at high recurrence risk, 5 (22%) with pending possible distant recurrence, and 2 with other cancers (skin and breast). The remaining four two-gene blood positive cases showed no sign of recurrence.
Conclusions: Following cancer treatment most (93%) patients show either no detectable methylated BCAT1 or IKZF1 or significantly reduced levels in blood plasma. Methylated IKZF1 and BCAT1 DNA in the blood correlated with local or distant recurrence or high risk of recurrence (83%) even if CEA was negative. The clinical utility of the 2-gene blood test for CRC recurrence monitoring should be further investigated.