[Association of RAS mutations in circulating cell-free DNA in the plasma with clinicopathological features of colorectal cancer].

OBJECTIVE: To detect RAS mutations in the circulating cell-free DNA (cfDNA) in the plasma and explore the their correlation with the clinicopathological features in patients with colorectal cancer. METHODS: Real-time PCR was used to detect RAS mutations in plasma cfDNA and matched tumor tissue DNA samples from 71 colorectal cancer patients. The correlation of RAS mutations with the clinicopathological features of the patients were analyzed. RESULTS: Of the 71 patients with colorectal cancer, 23 (32.39%) showed RAS mutations in the cfDNA and 36 (50.7%) showed RAS mutations in tumor tissue DNA, with a concordance rate of 76.06% in the results between the two samples (Kappa=0.523). RAS mutations in the cfDNA were not related to the patients' age (P=0.072), gender (P=0.320), tumor stage (IVa and IVb, P=0.450), primary tumor position (P=0.324), lung metastasis (P=0.237), CEA level (P=0.284) or CA199 level (P=0.427). The positivity rate of RAS mutations in plasma cfDNA was significantly higher in patients with liver metastasis than those without liver metastasis (P=0.045). CONCLUSION: Plasma cfDNA can be a reliable source of diagnostic DNA to replace the tumor tissue DNA for diagnosis of RAS mutations. RAS mutations in plasma cfDNA occur more frequently in colorectal cancer patients with liver metastasis.

Reversible posterior leukoencephalopathy syndrome induced by bevacizumab plus chemotherapy in colorectal cancer.

Reversible posterior leukoencephalopathy syndrome (RPLS) is a rare brain-capillary leak syndrome, characterized by clinical symptoms of headache, visual loss, seizures and altered mental functioning. This syndrome is usually reversible and is associated with hypertension, nephropathy, and use of immunosuppressive medication and cytotoxic agents. We describe two rare cases of RPLS occurring in colorectal cancer, both of which presented with coma, that we believe can be directly attributed to bevacizumab, a monoclonal antibody that inhibits the angiogenesis of tumours by specifically blocking vascular endothelial growth factor. We analysed the clinical features, risk factors and outcomes of RPLS in these two patients, and although no typical finding was identified on imaging examination, we found that inadequate blood pressure control was one of the risk factors leading to RPLS and that supportive treatment including intensive blood pressure control improved outcomes. Due to the increasing use of bevacizumab in colorectal cancer, clinicians should be aware of this potential complication.