No abstract

metastatic colorectal cancer and to examine the relationship between this phenomenon and survival rate of the patients.Methods: After receiving IRB approval, clinical information was collected on patients with metastatic colorectal cancer whose tumors exhibited RAS mutation and who were treated between 2010-2020 at Shamir Medical Center or Sourasky Medical Center. After calculating the ratio of the mutant allele and the wild-type allele, the tumours were classified as either MASI positive or MASI negative. We studied the prevalence of the RAS MASI phenomenon and looked for its effect on three variables: overall survival, disease-free survival and one-year survival.Results: We collected molecular and clinical information on 88 patients. The prevalence of RAS MASI among all patients in the study was 38.6%. Among the group of patients who were initially diagnosed with metastatic disease (stage 4), the incidence was higher and reached 47.7%. In terms of survival after one year, we found a statistically insignificant difference between the MASI group and the non-MASI group in the patients who first presented with stage 4 disease. The survival rate in the MASI group after one year was 76.3%, compared with 56.3% in the non-MASI group.Conclusions: RAS MASI is a clinically significant phenomenon among patients with metastatic colorectal cancer and a strong signal was seen in patients whose disease was initially diagnosed with distant metastasis. Among these patients, RAS MASI may be a negative prognostic factor in the first year of diagnosis, however further research is important to lead to statistically significant results.Legal entity responsible for the study: The authors.