Pre-Surgical MSI Testing for Young Patients

Digestive Disease Week 2011 Update

Finding colorectal cancer patients with Lynch syndrome helps both patients and their families to prevent cancer.

Lynch patients are at high risk for a second or third colon cancer, so identifying them before their colorectal surgery may change the operation planned.  Surgeons may want to remove the entire colon to prevent another colon cancer, and women may choose to have a hysterectomy during the same surgery to prevent endometrial cancer.

Because young patients are more likely to have Lynch syndrome, pathologists at the Mayo Clinic tested tumors from patients 50 years old or younger for microsatellite instability (MSI) after their surgery if they had not been tested preoperatively.

Comparing those with preoperative MSI testing to those whose tumors were tested after surgery gave the pathology team a chance to see if preoperative testing changed the surgical plan.

Between 2003 and 2008, 210 young patients with colorectal cancer had MSI testing, either before or after their surgery”

  • 13 percent had high microsatellite instability (MSI-H).
  • Two out of three (63 percent) of MSI-H patients had an inherited Lynch syndrome mutation.

Doctors knew before surgery that 16 patients had MSI-H tumors, but they only knew for sure that 2 of the 16 had Lynch syndrome because of genetic testing.  For the 16

  • 7 (43.8%) had at least one first-degree relative with colorectal cancer
  • 13 (81.3%) had any family history of colorectal cancer
  • Surgeons recommended that a complete colectomy be done at the time of their surgery for 15 of the 16.
  • 11 of 16 had colectomy performed.
  • 8 out of the 10 women had a hysterectomy.
  • 12 of 16 had genetic testing for Lynch syndrome done, 2 prior to surgery.
  • 9 of 16 (56.3%) tested positive for Lynch.

There were 12 patients who weren’t tested before surgery but tested MSI-H postoperatively.  For that group

  • 2 (16.7%) had a first degree relative with colorectal cancer
  • 5 (41.7%) had any family history of colorectal cancer
  • 1  had colectomy recommended prior to surgery and that individual did have a the colon removed.
  • The 1 female did not have a hysterectomy.
  • 4 out of the 12 had a genetic blood test for Lynch syndrome.
  • 1 was positive.

Jennifer Holder-Murray and her team concluded,

MSI-H status was found in 13% of young-onset colorectal cancer patients operated at our institution, and 63% of those tested, had germ-line mutations. Knowledge of MSI status preoperatively significantly influenced surgical management with an increase in total colectomy and hysterectomy compared to patients whose MSI-H status was discovered postoperatively. The absence of germ-line testing in MSI-H patients did not appear to influence surgical decision making.

SOURCE:  Holder-Murray, Digestive Disease Week 2011, Poster Session, Mo 1599,Impact of Preoperative Microsatellite Instability Testing On Surgical Management in Young-Onset Colorectal Cancer Patients: Results from a Reflex Testing Protocol.


  • Patients who are 50 and younger and have been diagnosed with colon or rectal cancer may want to discuss having their biopsy tissue tested for microsatellite instability (MSI) before they have surgery.
  • If MSI-High, they may want to have further blood testing for an inherited Lynch syndrome mutation.
  • Lynch positive patients should discuss a complete colectomy with their surgeons.  Women may want to have ovaries and uterus removed since they have a substantial (40 to 60 percent) lifetime risk of endometrial cancer and about a 12 percent risk of ovarian cancer.


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