Germline CDH1 variants in hereditary diffuse gastric cancer syndrome with focus on younger women

Trends in diffuse type of gastric cancer: focus on younger women

BACKGROUND

Gastric cancer (GC) incidence has been decreasing over the last decades; however, there are uncertainties in trends and proportional distribution of the diffuse type.

METHODS

GC incidence data were extracted from the population-based Friuli Venezia Giulia Cancer Registry. GC types (diffuse vs. others) were compared in relation to age at diagnosis, calendar years, and sexes.

RESULTS

Between 1995 and 2021, diffuse GC accounted for 10.2% of all GCs. The proportion was greater among individuals aged <45 years, 34.0% in women and 25.7% in men. An increasing proportion over time was observed, in particular in women (from 9.9% in 1995-2000 to 14.10% during 2011-2021). In the last decade (2011-2021), a decreased incidence of all GC was observed, reaching an age-standardized rate (world standard) of 1.4/100,000 for men and 1.2/100,000 for women. Rates of diffuse GC were 0.3/100,000 in younger population.

CONCLUSION

Although the overall GC incidence is decreasing, the percentage of diffuse GC is increasing in the younger population, particularly in women. Reasons for the increased proportion of diffuse-type GC within younger women remain uncertain, possibly related to the decreased exposure to risk factors for other GC histotypes.

Current advances and challenges in Managing Hereditary Diffuse Gastric Cancer (HDGC): a narrative review

More than 25 years ago, CDH1 pathogenic variants (PVs) were identified as the primary cause of hereditary diffuse gastric cancer (HDGC), an inherited cancer syndrome that increases the lifetime risk of developing diffuse gastric cancer (DGC) and lobular breast cancer (LBC). Since DGC is associated with a poor prognosis, a prophylactic total gastrectomy (PTG) is currently the gold standard for reducing the risk of DGC in CDH1 PV carriers. However, as germline genetic testing becomes more widespread, many CDH1 PV carriers have been identified, including in families with lower penetrance levels or without a history of gastric cancer (GC). When including these families, recent findings suggest that the cumulative lifetime risk of developing advanced DGC is much lower than previously thought and is now estimated to be 13-19%. This lower risk, combined with the fact that around one third of the CDH1 PV carriers decline PTG due to potential lifelong physical and psychological consequences, raises critical questions about the current uniformity in recommending PTG to all CDH1 PV carriers. As a result, there is a growing need to consider alternative strategies, such as endoscopic surveillance. However, despite the currently lower estimated risk of infiltrative (advanced) DGC, almost every PTG specimen shows the presence of small low-stage (pT1a) signet ring cell (SRC) lesions of which the behaviour is unpredictable but often are considered indolent or premalignant stages of DGC. Therefore, the primary goal of surveillance should be to identify atypical, deeper infiltrating lesions rather than every SRC lesion. Understanding the progression from indolent to more infiltrative lesions, and recognizing their endoscopic and histological features, is crucial in deciding the most suitable management option for each individual.

Points to consider regarding prophylactic total gastrectomy in germline CDH1 variant carriers

Pathogenic germline CDH1 mutation confers high risk for developing diffuse gastric and lobular breast cancers in asymptomatic carriers. In these individuals, the estimated gastric cancer risk at 80 years of age is up to 70% for males and 56% for females. Due to this high-risk predisposition, prophylactic total gastrectomy is considered a unique life-saving approach in germline CDH1 carriers, as endoscopy often fails to detect early stage diffuse gastric carcinoma. However, surgical indication is controversial in some clinical contexts, with possible contraindications. This review discusses points against and in favor of a more aggressive surgical approach for consideration during the decision-making process.