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Genetics of Colorectal Cancer (PDQ®): Genetics - Health Professional Information [NCI] - Psychosocial Issues in Hereditary Colon Cancer Syndromes

Table 15. Summary of Studies Evaluating Attitudes Toward, Interest in, or Intention to Use Assisted Reproductive Technology (ART) for FAPa, LSb, and PJSa continued...

Issues With Informed Consent for Microsatellite Instability (MSI) and Immunohistochemical (IHC) Tumor Testing

Advocacy for universal screening of all colorectal tumors for MSI and IHC to detect the absence of mismatch repair (MMR) proteins has increased.[31,32] This protocol could lead to increased identification of LS individuals and families;[33] however, there is an ongoing discussion about best practices for the informed consent process for this tumor testing.[34] MSI alone does not definitively establish a germline mutation in an MMR gene. IHC, on the other hand, can point to a specific underlying germline genetic defect because of the absent expression of a MMR protein (if methylation has been excluded). IHC results inform subsequent gene-specific mutation testing and therefore can be a surrogate for a LS diagnosis.[33,35]

It is generally advised that identification of genetic predisposition to cancer mandates explicit informed consent because of concerns for the possibility of insurance discrimination (irrespective of the Genetic Information Nondiscrimination Act of 2008), adverse psychological outcomes, and costs associated with further testing.[36,37] The Evaluation of Genomic Applications in Practice and Prevention working group specifically recommends obtaining informed consent for MSI or IHC testing.[31] Nevertheless, debate about this issue continues, partially because of pragmatic concerns surrounding the feasibility of obtaining such consent prior to the procedure. One proposed approach suggests a preparatory conversation informing patients prior to their procedure that CRC runs in families and that if their tumor has features characteristic of a heritable type, they will be contacted by a genetic health care provider for further assessment of the genetic basis of their cancer.[34] A cross-sectional survey of U.S. cancer programs (20 National Cancer Institute–designated comprehensive cancer centers and 49 community hospital cancer programs) found that, of those that performed MSI and/or IHC testing as part of standard pathologic evaluation at the time of colon cancer diagnosis in all or select cases, none required written informed consent prior to tumor testing.[38]

(Refer to the Informed Consent section in the PDQ summary on Cancer Genetics Risk Assessment and Counseling for more information.)

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