Investigations

1st investigations to order

oesophagogastroduodenoscopy with biopsy

Test
Result
Test

Oesophagogastroduodenoscopy with biopsy is the initial diagnostic test. It allows precise localisation of the primary tumour and acquisition of tissue for diagnosis, histological classification, and molecular biomarkers.[26][27]

The European Society for Medical Oncology (ESMO) recommends multiple biopsies (5-8) to confirm the representation of the tumour.[27]​ The National Comprehensive Cancer Network (NCCN) in the US recommends multiple biopsies (6-8) using standard size endoscopy forceps to provide adequately sized material for histologic and molecular interpretation, especially in the setting of an ulcerated lesion.[26]

Result

ulcer or mass or mucosal changes

CT of chest/abdomen/pelvis

Test
Result
Test

Chest, abdomen, and pelvis CT scans with oral and intravenous contrast are recommended for all patients to detect local or distant lymphadenopathy and metastatic disease or ascites.[26][27]

Result

metastatic lesions

FBC

Test
Result
Test

Initial laboratory tests should include FBC to assess for iron deficiency anaemia.[26][27]

Result

normal or microcytic anaemia

comprehensive metabolic panel

Test
Result
Test

Initial laboratory tests should include a renal function test and a liver function test to help determine suitable therapeutic options.[26][27]

Result

variable

H pylori testing/screening

Test
Result
Test

Screening should be performed in patients with early gastric cancer, and appropriate treatment must be given to eradicate the infection. H pylori testing of close family members is also recommended.[26]

Result

positive if H pylori is present

molecular and pathological tests

Test
Result
Test

Immunohistochemistry (IHC), in situ hybridisation, or targeted polymerase chain reaction should be considered first for the identification of biomarkers, followed by next-generation sequencing.[26]

Microsatellite instability (MSI) testing (by polymerase chain reaction or next-generation sequencing), or mismatch repair deficiency testing by IHC, should be conducted in newly diagnosed patients.[26]

Testing for HER2 overexpression using IHC or fluorescent in-situ hybridisation is recommended for all patients who have confirmed or suspected advanced/metastatic disease. PD-L1 testing by IHC may be considered in locally advanced, recurrent, or metastatic gastric cancer, to determine their eligibility for PD-1 inhibitors.[26]

Claudin 18.2 (CLDN18.2) testing is recommended for patients who have confirmed or suspected unresectable locally advanced, recurrent, or metastatic gastric cancer and in whom zolbetuximab is being considered.[26]

Result

HER2-positive or HER2-negative; MSI-high (MSI-H) or MSI-low (MSI-L) or MSI-stable (MSS); MMR-deficient (dMMR) or no evidence of deficient mismatch repair; PD-L1 expression: positive (CPS ≥1) or negative (CPS <1); CLDN18.2 positive or CLDN18.2 negative

Investigations to consider

endoscopic ultrasound

Test
Result
Test

Used to assess the proximal and distal extent of the tumour and provide accurate tumour and nodal assessment if no metastatic disease is detected by CT scan.[26][27]

Result

determines clinical tumour (T) and node (N) stage

laparoscopy

Test
Result
Test

Staging laparoscopy should be considered, as peritoneal and metastatic disease <5 mm in size may be missed, even with high-quality CT scans.

The European Society for Medical Oncology recommends laparoscopy with or without peritoneal washing for malignant cells for all patients with stage 1B to 3 potentially resectable gastric cancers, to exclude radiologically occult metastatic disease.[27]

The US National Comprehensive Cancer Network (NCCN) recommends laparoscopy with cytology for clinical stage T1b or higher to evaluate for peritoneal spread when considering local therapy, unless a palliative resection is planned.[26]

Result

metastatic lesions

PET/CT scan

Test
Result
Test

Combined PET/CT imaging may improve staging by detecting involved lymph nodes or metastatic disease. It should be considered for patients whose CT scans show locally advanced disease to rule out distant metastases, which would make them ineligible for curative therapy. The NCCN notes that combined fluorodeoxyglucose (FDG)-PET/CT imaging offers several potential advantages over FDG-PET or CT scans alone.[26]​ However, the accuracy of FDG-PET may be low in some gastric cancer types (e.g., diffuse and mucinous) because of low FDG uptake.[28][29]

Result

metastatic disease

liquid biopsy

Test
Result
Test

Can be used to evaluate circulating tumour DNA (ctDNA) by means of a blood test. Liquid biopsy can detect mutations/alterations or fusions in DNA shed from gastric cancer, therefore helping identify alterations that can be targeted by available treatments. A negative result does not exclude the presence of tumour mutations or amplifications and should, therefore, be interpreted with caution.[26]

Result

ctDNA-positive or negative

Use of this content is subject to our disclaimer