COLORECTAL CANCER (CRC)

Epidemiology: 3^rd most common cancer.

                        3^rd most deadly in U.S.

                        Most patients are > 50 years of age.

                        About 25% of patients have family history.

Genetics:

               _Familial Adenomatous polyposis (FAP): 

                 Autosomal dominant mutation of APC gene

                 and chromosome 5q. Two hit hypothesis.   

                100% progress to CRC.

               Thousand of polyps, pancolonic; always involves

                rectum.

               _Gardner’s Syndrome: FAP + osseous and soft

                 tissue tumor,retinal hyperplasia.

               _Turcot’s syndrome: FAP + malignant CNS

                  tumor.

               _Hereditary nonpolyposis colorectal cancer

                 (HNPCC/Lynch syndrome):

                 autosomal dominant mutations of DNA

                 mismatch repair genes. About 80% progress to

                 CRC. Proximal colon is always involves.

Additional risk factor: Inflammation Bowels Diseases (IBD), streptococcus bovis bacteriemia, tobacco use, large villous adenoma, juvenile polyposis syndrome, Peutz-Jegher’s syndrome.

Presentation:

                 Distal colon: obstruction, colicky pain,

                                           hematochezia.

                 Proximal colon: dull pain, iron deficiency

                                            anemia, fatigue.

Diagnosis: iron deficiency anemia in older males. Screen patients >50 years with stool  occult blood test and colonoscopy.“Apple core lesion” seen on barium enema x-ray.Carcinoembriogenic antigen (CEA) tumor marker.