a prospective cohort study has shown.
“In short, what we are putting forward with these data is that pathogenic/likely pathogenic (P/LP) variants in the CDH1 gene confer a very high risk, at the very least, of occult early-stage gastric cancer in patients with HLBC,” said Jeremy Davis, MD, of the surgical oncology program, Center for Cancer Research at the National Cancer Institute.
“So patients that are referred to as ‘HLBC’ due to a CDH1 variant should at least undergo annual endoscopic surveillance but the real questions is whether or not they should also consider prophylactic total gastrectomy – as many patients in our study did,” he said.
The study, which was published online Oct. 13, 2021, in, included a cohort of 151 families totaling 283 patients with a CDH1 pathogenic or likely pathogenic (P/LP) variant. Analyses were conducted on three patient groups, which included those with HLBC and a family history of breast cancer but no gastric cancer, those with hereditary diffuse gastric cancer (HDGC) but no history of breast cancer, and those with a family history of both gastric and breast cancer in the mixed group. Of these, 15.5% had a history of HLBC, 16.2% had a history of HDGC, and 52.6% made up the mixed group.
“We examined the HLBC group with specific attention to CDH1 genotype and prevalence of occult gastric cancer,” the authors explained. The group consisted of 31 families with 19 CDH1 variants, 10 of which were also present in the HDGC and mixed groups.
Among this group of patients, almost 73% underwent one or more surveillance endoscopies and on endoscopy, occult signet ring cell carcinoma was detected in over one-third of patients.
The median age at the time of endoscopic carcinoma detection was only 33 years.
“Nearly all of the patients with HLBC (93.8%) ... who elected for risk-reducing total gastrectomy owing to their underlying CDH1 P/LP variant harbored occult signet ring cell gastric adenocarcinoma on final pathology,” investigators observed.
The median age at the time patients elected to undergo total gastrectomy was 50 years.
The prevalence of occult gastric cancer among asymptomatic patients in the HDGC group was similarly high, affecting almost 95% of this group of patients.
Some 18 out of 19 CDH1 P/LP variants were responsible for this high prevalence of occult gastric cancer, as the investigators pointed out.
“Hereditary cancer risk is informed by the presence of a germline gene variant more so than by family history of cancer,” the authors stressed. “[And we found that] germline CDH1 P/LP variants appear to have a highly penetrant gastric phenotype irrespective of family history.”
Given this finding, the authors stressed that it is “paramount” patients previously assigned a diagnosis of HLBC not be excluded from undergoing gastric cancer risk assessment and counseling.
Furthermore, “the mere presence of a germline CDH1 P/LP variant, regardless of family history, may be reason enough to consider prophylactic total gastrectomy,” the authors wrote.
Limitations of the study included the fact that the disease phenotype was established from family pedigrees which has the potential for recall bias by family members.
The study was supported in part by the Intramural Research Program of the National Cancer Institute. None of the authors had conflicts of interest to disclose.