Microsatellite instability and B-type Raf proto-oncogene mutation in colorectal cancer: Clinicopathological characteristics and effects on survival

  • Sebnem Batur Cerrahpasa Medical Faculty, Istanbul University
  • Dogu Vuralli Bakkaloglu Cerrahpasa Medical Faculty, Istanbul University
  • Nuray Kepil Cerrahpasa Medical Faculty, Istanbul University
  • Sibel Erdamar Cerrahpasa Medical Faculty, Istanbul University
Keywords: Microsatellite instability, DNA mismatch repair genes, B-type Raf proto-oncogene mutation, survival, polymerase chain reaction, immunohistochemistry


Prognostic significance of microsatellite instability (MSI) status and B-type Raf proto-oncogene (BRAF) mutation in colorectal cancer is controversial. The aim of this study was to examine the clinical and pathological characteristics associated with microsatellite stability and the effect of MSI and BRAF mutation on the survival of patients with colorectal cancer. The study included 145 colorectal cancer cases. All the patients were examined for DNA mismatch repair (MMR) proteins with an immunohistochemical method. Molecular assessment of MSI was available in a subset of 41 patients. In addition, BRAF mutation analysis was performed in 30 cases. Immunohistochemically, MMR deficiency was present in 28 (19.3%) patients. Female gender (p = 0.001), lesion size ≥5 cm (p = 0.013), Crohn-like response (p = 0.035), and right-sided localization (p < 0.001) were significantly more frequent among MMR-deficient patients. The overall survival was 44.1 ± 5.1 months (95% confidence interval [CI], 33.7-54.4). Multivariate analyses identified only high tumor grade as an independent predictor of poor overall survival: odd ratio, 6.7 (95% CI 2.1-21.7), p = 0.002. In the subset of patients with available BRAF assessment (n = 30), a negative BRAF status was associated with better survival when compared to a positive BRAF status (36.7 ± 2.1 vs. 34.1 ± 7.2 months, p = 0.048). The sensitivity and specificity of the immunohistochemical method in predicting positive MSI status, with the molecular method as a reference, were 85.7% (95% CI: 56.2%-97.5%) and 88.9% (95% CI: 69.7%-97.1%), respectively. BRAF appears to be a significant predictor of a worse outcome in patients with colorectal cancer. Further studies with a large spectrum of clinical and biological variables are warranted.


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Author Biographies

Sebnem Batur, Cerrahpasa Medical Faculty, Istanbul University
Department of Pathology
Dogu Vuralli Bakkaloglu, Cerrahpasa Medical Faculty, Istanbul University
Department of Pathology
Nuray Kepil, Cerrahpasa Medical Faculty, Istanbul University
Department of Pathology
Sibel Erdamar, Cerrahpasa Medical Faculty, Istanbul University
Department of Pathology


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Microsatellite instability and B-type Raf proto-oncogene mutation in colorectal cancer: Clinicopathological characteristics and effects on survival
How to Cite
Batur S, Vuralli Bakkaloglu D, Kepil N, Erdamar S. Microsatellite instability and B-type Raf proto-oncogene mutation in colorectal cancer: Clinicopathological characteristics and effects on survival. Bosn J of Basic Med Sci [Internet]. 2016Nov.10 [cited 2020Aug.15];16(4):254-60. Available from: http://www.bjbms.org/ojs/index.php/bjbms/article/view/1238