"In a study using the world's largest dataset of its kind, we found that in terms of association with increased risk of colorectal cancer, family history of colorectal carcinoma in situ (adenoma with high-grade dysplasia) is as important as family history of invasive colorectal cancer," Dr. Mahdi Fallah of the National Center for Tumor Diseases (NCT) and the German Cancer Research Center (DKFZ) in Heidelberg, Germany, told Reuters Health.
"This has an important implication in early screening of those with family history of any colorectal tumor," he added by email.
Dr. Fallah and his colleagues collected data from Swedish family-cancer datasets and calculated standardized incidence ratio (SIR) and cumulative risk of CRC in first- and second-degree relatives of people with CCIS. Of the more than 12.8 million persons with available genealogical data, 173,796 were diagnosed with CRC and 40,558 with CCIS.
As reported in the Journal of the National Comprehensive Cancer Network, the lifetime (0-79 years) cumulative risk of CRC in first-degree relatives of patients with CCIS was 6.5%, a 1.6-fold increase (95% confidence interval, 1.5 to 1.7). Similarly, for first-degree relatives of patients with CRC, the risk was 6.7% (SIR, 1.6; 95% CI, 1.6 to 1.7).
Significantly elevated risk of CRC was also found in half-siblings of patients with CCIS (SIR, 1.9) and half-siblings of patients with CRC (SIR, 1.7).
Dr. Lyen C. Huang, an assistant professor of surgery and a co-leader of the Huntsman Cancer Institute Colorectal Cancer Research Group at the University of Utah, in Salt Lake City, said, "Colorectal cancer is the third-most common cancer in the world; and the incidence is rising, particularly in young adults below the usual age of screening (45-50 years old). Identifying young high-risk individuals will allow us to tailor our screening practices to diagnose and treat the cancer earlier."
The new "analysis was very robust and took into account many potential factors such as different combinations of family history," said Dr. Huang, who was not involved in the study. "The study also looked at patients over a long period of time. Whether these risks exist in other countries and populations remains to be seen."
"We still don't know how much of the familial risk factors are due to genetics as opposed to dietary, socioeconomic, and environmental factors," he told Reuters Health by email.
His advice to clinicians? "First, we need to be more precise when documenting family history of colorectal carcinoma in situ and cancer, and the age of diagnosis. Second, we need to counsel patients who are diagnosed with carcinoma in situ about the risk to their family members. Third, we may consider earlier colorectal cancer screening for first-degree family members and half-siblings of those diagnosed with carcinoma in situ."
Julie Culver, director of genetic counseling at the University of Southern California (USC) Norris Comprehensive Cancer Center in Los Angeles, advises patients about colorectal-cancer screening.
"Screening for colorectal cancer, most notably colonoscopy screening, saves countless lives," Culver, who also was not involved in the study, told Reuters Health by email. "Family history of cancer is an important risk indicator, but previous studies have not allowed for risk calculation for relatives of patients with colorectal cancer in-situ."
"The strength of the study is that it used an extremely large tumor registry in Sweden that is associated with family history data collection, and that the family history records are frequently updated," she noted. "The weakness is that the findings were from one country and the results may be somewhat different in other ethnic or racial groups. Also, the classification of colon cancer in situ may not be uniform; therefore the diagnosis may be somewhat subjective."
SOURCE: https://bit.ly/3CU8AHk Journal of the National Comprehensive Cancer Network, online September 13, 2021.
By Lorraine L. Janeczko
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