Project 466815

Lynch syndrome (LS) is the most common cause of inherited colorectal cancer (CRC). LS is caused by inherited changes in one of four DNA mismatch repair (MMR) genes, resulting in an increased risk for developing numerous cancers. When a patient is diagnosed with CRC, they are often screened for LS. As LS is caused by changes in MMR genes, a sample of the tumour is examined for MMR proteins. CRC without the presence of MMR proteins are considered MMR-deficient. Only some patients with MMR-deficient CRC, however, are found to have an inherited mutation in an MMR gene that is consistent with a diagnosis of LS. The remaining group have unexplained MMR deficiency and a diagnosis of LS cannot be confirmed; patients are left without a definitive diagnosis. Using a combination of surveys and qualitative interviews, I will evaluate the ability of these patients to cope with their uncertain diagnosis and what their diagnosis has meant for their family members. For each patient, I aim to evaluate their knowledge and recollection of their results, the information they received from the Genetics clinic, and how screening guidelines align with their current monitoring routines. Patients with MMR-deficient tumors are often treated as if they have LS and are subjected to rigorous, and often unnecessary, cancer screening. Patients who do not have inherited variants do not require the same level of observation, yet current practices lead to many patients being over-screened. Characterizing the impact of uncertain MMR-deficient results may encourage the implementation of additional genetic testing to clarify a diagnosis for these patients and reduce screening recommendations. Findings from this study may also impact how information is provided to individuals with other uncertain diagnoses.