Stomach cancer, also known as gastric cancer, involves abnormal cell growth in the stomach lining. Accurately diagnosing and staging the cancer, which means determining its presence and spread, is crucial for guiding treatment decisions. Imaging techniques provide important visual information for this assessment.
MRI’s Role in Stomach Cancer Detection
Magnetic Resonance Imaging (MRI) uses strong magnets and radio waves to create detailed images of organs and soft tissues. For stomach cancer, MRI provides information on tumor presence, size, and location. Its high soft tissue contrast is valuable for assessing stomach wall layers and identifying tumor infiltration.
MRI is useful for local staging, determining the depth of tumor invasion into the stomach wall (T-staging). Its accuracy for T-staging in gastric cancer can range from 71.4% to 88%. MRI also helps assess regional lymph node involvement (N-staging), with reported accuracies between 52% and 68%. Advanced MRI techniques may further improve the detection of metastatic lymph nodes.
Beyond local assessment, MRI helps detect distant cancer spread (M-staging). It effectively identifies metastases in organs like the liver and peritoneum due to its excellent soft tissue visualization. MRI can detect small liver lesions that other imaging methods might miss. Diffusion-weighted MRI has shown promising diagnostic performance for peritoneal involvement.
Limitations of MRI for Stomach Cancer
Despite its strengths, MRI has limitations for stomach cancer detection and staging. It may not be sensitive enough to identify very early-stage or superficial cancers, especially if they are small or flat. The detection rate for early gastric cancer can be low, with some studies showing it to be as low as 16% for certain early-stage tumors.
Distinguishing between non-cancerous conditions like inflammation or ulcers and malignant tumors on MRI can be difficult. Inflammation around a lesion can also affect tumor invasion assessment. Motion artifacts, due to stomach and bowel movements or breathing during the scan, can obscure details or make image interpretation challenging.
MRI scans can also be more expensive and less widely available compared to other imaging methods. While MRI can show lymph nodes, differentiating between enlarged nodes due to inflammation and those containing cancer cells can be complex, affecting its specificity for N-staging.
Other Diagnostic Tools for Stomach Cancer
Stomach cancer diagnosis and staging involve a range of specialized tools. Upper endoscopy with biopsy is the primary and definitive method for diagnosis. This procedure allows direct visualization of the stomach lining and collection of tissue samples, which confirms the presence of cancer.
Computed Tomography (CT) scans are widely used for broader staging of stomach cancer. CT can assess regional lymph nodes and detect distant metastases in areas such as the lungs or bones. It is a relatively fast and accessible imaging modality, often serving as the standard radiologic tool for overall staging.
Endoscopic Ultrasound (EUS) uses an endoscope with an ultrasound probe to provide highly detailed images of the stomach wall and surrounding structures. EUS is particularly accurate in determining the depth of tumor invasion and assessing nearby lymph nodes, especially for early-stage cancers. Its accuracy for T-staging can range from 60% to 100%, and for N-staging, it can be between 50% and 85%.
Positron Emission Tomography (PET) scans detect metabolically active cancer cells throughout the body. PET scans are primarily used to identify distant metastases or recurrence, and can also help assess treatment effectiveness. While useful for detecting distant spread, PET’s sensitivity for early gastric cancer and some types of lymph node metastases can be low.
The Diagnostic Pathway for Stomach Cancer
The diagnostic journey for stomach cancer typically begins with suspicious symptoms. The first definitive step to confirm a diagnosis is usually an upper endoscopy with a biopsy of any suspicious areas. This tissue analysis is essential for identifying cancer cells.
Once cancer is confirmed, imaging tests determine the extent of the disease, a process called staging. CT scans are often performed initially for a broad overview of potential spread, given their speed and widespread availability. Endoscopic ultrasound (EUS) is then frequently employed for detailed local assessment, providing precise information about the tumor’s depth of invasion and involvement of nearby lymph nodes, especially for early tumors.
MRI often plays a specific role in this pathway, particularly when more detailed soft tissue contrast is needed. It is valuable for assessing potential liver metastases or peritoneal involvement, or when CT results are unclear. PET scans are typically used to identify distant spread of cancer not visible on other scans or to check for recurrence. The entire diagnostic and treatment planning process usually involves a team of specialists.