Hereditary Diffuse Gastric Cancer – Surveillance or Prophylactic Gastrectomy (#68)
The management of Hereditary Diffuse Gastric Cancer (HDGC) has advanced dramatically in the 15 years since CDH1 mutations were first described in three New Zealand gastric cancer families. HDGC is a challenging familial cancer syndrome to manage and clinicians in New Zealand had to grapple early on with the management of 10 families, including a large family with a particularly early age of onset. CDH1 mutation carriers have a >80% risk of developing DGC and a 60% risk of lobular breast cancer by 80 years. Intestinal-type gastric cancer is not part of the syndrome.
Currently the only way to eliminate the risk of gastric cancer is prophylactic total gastrectomy, an operation with not insignificant mortality and morbidity risks, but none-the-less, now an established part of the management algorithm in HDGC. In almost all gastrectomy specimens from young HDGC patients, multiple microscopic foci of early (T1a) signet-ring cell carcinoma have been found, with 100-300 foci in some stomachs. This almost 100% penetrance for early foci in young carriers is in stark contrast to the lifetime cumulative risk, which implies the vast majority of early lesions must have a very indolent course.
Surveillance endoscopy is controversial in HDGC and far from a fail-safe technique. It does have a role in certain circumstances, but no long-term observational or randomized trial data exist. A chromo-endoscopic surveillance program was initially trialled in New Zealand and facilitated detection of foci, but now white-light endoscopy alone is carried out. Confocal endoscopy has been used in Melbourne HDGC patients. Given the diffuse morphologically of this type of gastric cancer, it will likely prove very difficult to develop a surveillance modality that is sufficiently sensitive to mean surveillance is considered safe.
International consensus guidelines on HDGC have been published, the most recent in 2008. In 2004 age-specific guidelines from New Zealand recommended a youngest age for genetic testing of 16y, surveillance gastroscopy from 16y and prophylactic gastrectomy after age 20y. In HDGC families where the age of onset is not so young, different age-specific recommendations may be appropriate.