(307) Epidemiology and diagnostic landscape for gastroesophageal adenocarcinomas with a HER2 focus

Background: : There is limited evidence on the epidemiology of gastric cancer (GC), esophageal cancer (EC) and gastroesophageal junction (GEJ) cancer (collectively known as gastroesophageal adenocarcinomas [GEAs]) and on laboratory diagnostic methods used to characterize GEA, particularly in patients with HER2+ status.

Objective: : A targeted literature review was conducted to retrieve evidence on incidence, prevalence, mortality, and survival in GEA and to characterize diagnostic methods used for GEA, with an emphasis on HER2+ status.

Methods: : Embase® and MEDLINE® were searched from 2014 to July 2024, without restrictions on country or language. These were supplemented with data from 2022 Global Cancer Observatory (GLOBOCAN) in key markets – the US, Canada, Japan and EU5.

Results: : 32 studies presenting HER2 positivity rates in patients with GEA were included from 2,308 initial records. The majority of epidemiological evidence in HER2+ GEA came from Asia (8 studies). HER2+ prevalence in patients with GEA ranged from 13.6% in Brunei Darussalam to 47.9% in China, and from 6% in Latin America to 14% in Europe. Five-year survival rates were higher in GC as compared to EC across geographies, irrespective of HER2+ status. Epidemiological data for all-comers GEA (irrespective of HER2+ status) from GLOBOCAN indicated global crude incidence rate of 12.3 per 100,000 for GC and 6.5 per 100,000 for EC. Incidence rates were higher in males than females for GC (15.8 vs 8.7 per 100,000) and EC (9.2 vs 3.7 per 100,000). Five-year prevalence rates of GC were considerably higher in Japan (274.6 per 100,000) compared with EU5 (11.4–27.7 per 100,000), Canada (14.5 per 100,000) and US (11.2 per 100,000). Mortality rates were higher with EC than GC in US (2.4 vs 1.6 per 100,000), UK (4.9 vs 2.3 per 100,000), and Canada (2.8 vs 2.4 per 100,000). Among the 32 studies in patients with HER2+ GEA, HER2 status was tested most commonly by combining immunohistochemistry (IHC) and in situ hybridization (ISH) (14 studies). High concordance rates were reported for HER2 positivity assessed using next generation sequencing with ISH (up to 98.3%) or IHC with ISH (up to 99.5%). Evidence on epidemiology and diagnostic performance for PD-L1 expression in patients with HER2+ GEA was limited.

Conclusions: : This review presents variability in GEA prevalence, incidence and mortality rates by geography, gender and GEA subtype. High concordance was observed with the use of IHC and ISH techniques in determining HER2+ status in GEA.

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