Background: Hereditary diffuse gastric cancer (HDGC) syndrome results most often from a mutation in the CDH1 tumor suppressor gene and confers a 56-70% lifetime risk of gastric cancer. In asymptomatic carriers HDGC is characterized by multiple foci of signet ring cancer cells (SRCC) throughout the gastric mucosa. Because SRCC foci are less than 1 mm in diameter, and often make up less than 2% of the gastric mucosa, they are undetectable on standard screening endoscopy. International consensus guidelines recommend thorough white light endoscopic gastric mapping with a systematic method for gastric biopsies. Despite a painstaking approach to gastric mapping, retrospective analyses have demonstrated a low rate of detection and poor sensitivity of standard white light endoscopy for detecting occult cancer cells. Therefore, a more sensitive cancer screening tool is needed for these high-risk patients. Confocal endoscopic microscopy (CEM) allows for real-time, in vivo histologic imaging of gastrointestinal mucosa during upper endoscopy. Clinical application has demonstrated the ability of CEM to differentiate normal mucosal cells and cancer cells.
Methods: A phase II clinical trial is currently underway to compare CEM to standard endoscopic gastric mapping in an effort to reduce the false negative detection rate of SRCC in patients diagnosed with HDGC. After an upper endoscopy with gastric mapping is performed, patients will undergo probe-based CEM. The endoscopist will scan the anatomic zones of the stomach in a similar fashion to the systematic gastric mapping approach. Any abnormal areas visualized with the CEM probe will be biopsied and sent for permanent pathologic analysis. The primary endpoint is to determine if CEM affords a higher sensitivity for detection of SRCC in CDH1 germline mutation carriers compared to white light endoscopy with gastric mapping.
Discussion: This novel screening technique is expected to provide greater sensitivity for detecting occult cancer in patients with HDGC, thereby improving cancer risk-assessment and overall cancer care.
Trial registration: ClinicalTrials.gov NCT03648879 (registration date: August 28, 2018, clinicaltrials.gov).
Keywords: CDH1; confocal endomicroscopy; gastric cancer.