Although being obese increases risk for most colon and rectal cancers, the connection isn’t true in all types of colorectal cancer.

Cancers that are linked to microsatellite instability (MSI) don’t appear to be influenced by obesity, strengthening the belief that MSI cancers come about differently than the average colorectal cancer.

Overall, in a recent study, body mass index and weight gain during adult life increased risk of colorectal cancer by about 30 percent for men and 20 percent for women. However, increased risk was limited to microsatellite stable or microsatellite low tumors. Read the rest of this entry »

You may have heard the exciting data on PARP inhibitors for patients with mutations in the BRCA genes reported at ASCO 2009. Patients who carry these mutations are deficient in DNA repair which makes them very sensitive to PARP inhibitors which play a significant role in DNA repair.

Why does that matter for colon cancer? Well, the genetic predisposition HNPCC is caused by another DNA repair deficiency linked to mutations in MLH1, MSH2, MSH6, PMS1 and PMS2. The landmark sign for mismatch repair deficiency is microsatellite instability also called MSI. Read the rest of this entry »

Since the last ASCO meeting in June 2008 not only has KRAS made headlines but also microsatellite instability (MSI).

Microsatellite instability has developed into the most important prognostic and predictive marker for patients with stage II colon cancer. Recent studies presented by Dr. Daniel Sargent at ASCO showed that patients with stage II colon cancer who have microsatellite instability did not benefit from 5-FU chemotherapy. Therefore these patients with no risk factors such as clinical obstruction, lymphovascular invasion, poorly differentiated adenocarcinoma, or insufficient lymph node collection should not receive 5-FU. Read the rest of this entry »