Oncologists are always trying to define prognosis in assessing need for treatment and intensity of treatment. Much has been accomplished in analyzing the prognosis of colon cancer, especially with regard to genetic mutations in the so-called mismatch repair gene. Now comes a large analysis from Italy, published in JAMA Oncology. The authors looked at sidedness as a prognostic factor — that is, whether the tumor was found in the right side versus left side of the colon. There has been increasingly appreciated a divide in these two locations: right-sided tumors are usually silent, present only with iron deficiency anemia. Clinical symptoms such as pain or obstruction occur very late. Red blood in the stool is rare. Left-sided tumors cause more pain, bleeding and symptoms related to bowel obstruction. Right-sided tumors are more likely associated with genetic mutations related to familial clusterings. The authors found that overall survival was significantly higher with left-sided tumors and feel that sidedness should be taken into consideration when deciding what, if any, adjuvant therapy is required. Click here for the abstract of the article. By filling out the form to the right Dr. Stark can send you the entire article.
Dr. Stark weighs in: sidedness is probably a surrogate marker for the biologic differences in tumors in the right and left sides of the colon. It may not have much if any independent significance. Nonetheless the study reminds us that colon cancer is not a homogenous disease.