By: David Shifrin, PhD Science Writer, Filament Life Science Communications
The value of genetic counseling for both patients and families has been reinforced by a recent study on colorectal cancer out of MD Anderson Cancer Center.
The study, titledHigh Prevalence of Hereditary Cancer Syndromes in Adolescents and Young Adults With Colorectal Cancer and published in the Journal of Clinical Oncology, looked at the clinical and genetic characteristics of young (35 years old and younger) patients diagnosed with CRC. The goal was to get a better grip on the profiles of these individuals, who are traditionally underrepresented in studies of the disease.
Patients were enrolled in the study following CRC diagnosis and subsequent genetic counseling. Importantly, family history (or lack thereof) was not a factor in whether individuals were included in the study. This point is notable because the goal was to investigate the specific clinicopathologic and genetic features of anyone diagnosed at a young age, rather than skew the results towards those with specific characteristics (such as family history of the disease).
Overall, the study authors found a hereditary cancer syndrome in more than a third of the enrollees. This was dramatically higher than the 2-5% that occurs across the entire population of CRC patients. In other words, younger patients diagnosed with CRC are far more likely to have a hereditary syndrome than those who are older.
Interestingly, the cancers in individuals without a known hereditary component were on average more advanced and/or metastatic than those in the hereditary group. The authors suggest that this is a result of increased screening in the latter cohort due to known family history.
Ultimately, the high percentage of hereditary syndromes led the authors to recommend genetic counseling for all young (≤35) CRC patients. This includes individuals with no known family history of the disease, and those who don’t display abnormalities in their tumor pathology results (e.g. microsatellite instability and immunohistochemistry). Enough of the study participants were found to have hereditary mutations in the absence of a known family history that it is worth broadly recommending counseling for young patients during the course of CRC clinical care. Of course, this is in large part to help protect family members who might be at risk for CRC despite not having a personal or familial history of the disease.
The study methodology is another great example of the seamless interaction between genetic testing, counseling, and clinical assessment. Using the clinical manifestation of each case as a guide, the patients received “syndrome-specific genetic testing.” If the genetic and pathological results of these assessments warranted, genetic testing was then recommended for family members.
However, the above raises another interesting question raised by this study. Namely, is there a potential value to standardizing genetic testing regimes for certain diseases? The authors note that their participants did not all receive the same testing, “so there may be patients in this cohort whose underlying hereditary predispositions were not identified.” Though it certainly makes sense from a clinical and economic standpoint to test individuals based on their specific circumstances, there is a value on the research side to standardizing testing. Though not a major component of the study at hand, this issue does highlight the common tension between research needs and individual clinical practice.