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AAMC practice guideline for universal screening of new colorectal cancer patients with molecular testing for Lynch Syndrome (LS)

by Medical Staff Office on July 29, 2014

The AAMC Laboratory Utilization Committee, after consultation with representatives from gastroenterology, hematology/oncology, colorectal surgery, and our genetic counselor, endorses a policy of universal molecular tumor testing for Lynch Syndrome in newly diagnosed colorectal cancer patients under 70 years of age.  After reviewing literature on this topic, the most reasonable and cost-effective strategy seems to be screening for mismatch repair genes using immunohistochemistry with reflex testing for BRAF V600E mutation if MLH1 is absent.  Loss of expression in any of the MMR genes (in the absence of a BRAF mutation) should prompt consultation with a genetic counselor for consideration of additional testing. This screening strategy should detect approximately 97% of cases.  Furthermore, it is recommended that testing be obtained at the time of diagnostic biopsy so the information is available prior to surgery, as a diagnosis of LS may change surgical options (hysterectomy in females and extended colectomy in males).  We recommend gastroenterologists adopt these guidelines when they have a new colorectal cancer diagnosis in their endoscopy center. Any new diagnoses of colonic adenocarcinoma made at AAMC in patients less than 70 years of age will automatically be sent for MMR profile with reflex to BRAF if MLH-1 is borderline or lost. This policy is meant to serve as a practice guideline.  Other testing approaches at the time of initial diagnosis may be equally reasonable at the discretion of the gastroenterologist or surgeon.  Thanks to Drs. Steve Proshan, Barry Cukor, and John Neuman along with Ashley Allenby, genetic counselor for their review and input.

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