Study Finds One-Third of Colorectal Cancers Diagnosed Before Age 35 Are Hereditary
Although the prevalence of genetic risk factors, such as Lynch syndrome and familial adenomatous polyposis, has been studied in the general population of individuals with colorectal cancer, patients diagnosed as adolescents and young adults are not well represented in colorectal cancer studies. A study by Mork et al investigating the extent of hereditary cancer syndromes and family history of cancer in patients diagnosed with colorectal cancer at age 35 or younger has found that 35% of the patients had an identifiable hereditary cancer syndrome.
The results of the study suggest that these patients should undergo genetic counseling to determine if their families are at an increased genetic risk for colorectal cancer. The study is published in the Journal of Clinical Oncology.
Study Methodology
The researchers reviewed data from 193 patients who were diagnosed with colorectal cancer at 35 years or younger and had been evaluated by genetic counseling at The University of Texas MD Anderson Cancer Center in Houston from 2009 to 2013. Data were collected regarding demographics, clinicopathologic information, tumor and genetic testing, and family history. Patients with an identified hereditary cancer syndrome were compared with those without a syndrome.
Study Findings
Of the 193 patients with evaluable data, 35% had an identifiable hereditary cancer syndrome, including 23 with Lynch syndrome, 22 with mutation-negative Lynch syndrome, 16 with familial adenomatous polyposis, two with constitutional mismatch repair deficiency, two with biallelic MUTYH mutations, and one with Li-Fraumeni syndrome.
Patients without a hereditary syndrome more frequently presented with metastatic disease, whereas patients with a syndrome were more likely to present at earlier stages and to have a family history of cancer. Nevertheless, a substantial proportion of the hereditary syndromes (19%) were diagnosed in individuals with no family history of the disease.
“We were very surprised to find that 35% of that population of patients had a genetic disease, although we hypothesized the proportion would be higher in this age group relative to the general population,” said Eduardo Vilar-Sanchez, MD, PhD, coauthor of the study and Assistant Professor in the Department of Clinical Cancer Prevention at MD Anderson Cancer Center, in a statement. “Based on our findings, patients under the age of 35 need to be evaluated by a genetic counselor. Period. The translation of that information extends well beyond the patient, as there are tremendous benefits from being able to share genetic risk with their parents, siblings, and many other family members.”
The researchers concluded: “Patients diagnosed with [colorectal cancer] at 35 years or younger have a higher frequency of hereditary predispositions to [colorectal cancer] than the general population of patients with [colorectal cancer]. Hereditary syndromes in these patients are not limited to [Lynch syndrome] or [familial adenomatous polyposis], nor to those with a family history of cancer. Adolescent and young adult patients with [colorectal cancer] should be referred for a hereditary cancer work-up and may benefit from the use of comprehensive hereditary [colorectal cancer] genetic testing panels, especially in the absence of a clinical phenotype or with normal [microsatellite instability] and [immunohistochemistry] tumor studies.”
Eduardo Vilar-Sanchez, MD, PhD, of MD Anderson Cancer Center, is corresponding author of this study.
Funding for this study was supported by the Feinberg Family Fund. The study authors reported no conflicts of interest.
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