Gastrointestinal Imaging

What Imaging Is Best for Surveillance of Adult Gastric Adenocarcinoma?

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What Imaging Is Best for Surveillance of Adult Gastric Adenocarcinoma?

It’s a busy Tuesday afternoon in the oncology clinic. Your next patient is a 68-year-old man, two years out from a subtotal gastrectomy and adjuvant chemotherapy for stage II gastric adenocarcinoma. He feels well and has no new complaints, but his scheduled surveillance visit is due. You need to decide on the appropriate imaging to screen for asymptomatic recurrence, balancing the need for detection with the risks of repeated radiation exposure. This clinical workflow article addresses this exact decision point: selecting the right imaging for routine surveillance in an adult with a history of treated gastric adenocarcinoma.

According to the American College of Radiology (ACR) Appropriateness Criteria, for this specific scenario, a CT abdomen and pelvis with IV contrast is rated Usually appropriate.

Who Fits This Clinical Scenario?

This guidance applies specifically to adult patients undergoing routine, scheduled surveillance for previously treated gastric adenocarcinoma. The key inclusion criteria are:

  • An established diagnosis of gastric adenocarcinoma.
  • Completion of definitive treatment (e.g., surgery, chemotherapy, radiation) with curative intent.
  • The patient is currently asymptomatic and being monitored at a scheduled interval for potential recurrence.

It is crucial to distinguish this surveillance scenario from other, similar clinical presentations that require a different imaging approach. This article does not apply if the patient is:

  • Undergoing initial staging: A newly diagnosed patient who has not yet been treated requires a comprehensive staging workup to determine the extent of disease, which is covered in a separate ACR variant.
  • Being evaluated immediately post-treatment: Imaging performed shortly after a course of therapy to assess treatment response has different considerations than long-term surveillance.
  • Presenting with new symptoms concerning for recurrence: A patient with new abdominal pain, weight loss, or other specific symptoms may require a more urgent or tailored diagnostic workup, potentially including different modalities.

Applying surveillance guidelines to these other scenarios can lead to inappropriate or incomplete evaluation.

What Diagnoses Are You Working Up in This Scenario?

Surveillance imaging aims to detect asymptomatic recurrence when it is potentially still manageable. The differential diagnoses, or the primary targets of the imaging study, are manifestations of recurrent gastric cancer.

Locoregional Recurrence: This is a primary concern and involves the return of cancer at or near the original tumor site. This can include the gastric remnant, the surgical anastomosis, or the regional lymph node basins (e.g., perigastric, celiac, para-aortic). Imaging must be able to differentiate subtle soft tissue thickening and enhancing nodules from normal post-surgical changes.

Peritoneal Carcinomatosis: Gastric cancer has a propensity to spread along the surfaces of the abdominal cavity. This can manifest as subtle peritoneal thickening, small nodules on the omentum or bowel surfaces, or the development of malignant ascites. Detecting early-stage peritoneal disease is a key goal of surveillance.

Distant Metastases: The most common site for distant spread of gastric cancer is the liver. Hepatic metastases often appear as hypo-enhancing lesions on contrast-enhanced CT. Other potential sites include distant lymph nodes, the adrenal glands, and the lungs (though a dedicated chest CT is a separate consideration, the lung bases are included on an abdominal CT).

Benign Post-Surgical Changes: A critical part of the differential is distinguishing true recurrence from expected post-operative findings. This includes surgical clips, inflammatory changes, fibrosis, and adhesions, which can sometimes mimic tumor recurrence. Careful comparison with prior imaging studies is essential.

Why Is CT Abdomen and Pelvis with IV Contrast the Recommended Study?

The ACR designates CT of the abdomen and pelvis with intravenous contrast as “Usually appropriate” because it provides a comprehensive, rapid, and widely available method for evaluating the key sites of potential recurrence in gastric cancer.

The rationale for its high rating stems from its diagnostic capabilities. Intravenous contrast is essential, as it opacifies blood vessels and enhances solid organs and abnormal tissues. This allows for the clear depiction of hypervascular or hypovascular liver metastases, enhancing peritoneal nodules, and enlarged, enhancing lymph nodes that signify recurrence. Without IV contrast, these findings can be easily missed, rendering a non-contrast CT “Usually not appropriate” for this indication.

This modality offers an excellent balance of spatial resolution and scan time, providing detailed anatomical information of the entire abdomen and pelvis in a single, brief acquisition. This is sufficient to assess the surgical bed, liver, adrenal glands, peritoneum, and key nodal stations.

In contrast, other imaging modalities are rated lower for routine surveillance:

  • MRI abdomen and pelvis without and with IV contrast is rated “Usually not appropriate.” While MRI offers excellent soft-tissue contrast and avoids ionizing radiation, it is generally more time-consuming, expensive, and susceptible to motion artifacts. For the specific task of routine surveillance, it does not typically offer a significant diagnostic advantage over a well-performed CT to justify these trade-offs.
  • FDG-PET/CT is rated “May be appropriate.” This modality combines functional information (metabolic activity) with anatomy and can be highly sensitive for detecting recurrent cancer. However, it involves a higher radiation dose (☢☢☢☢ 10-30 mSv) and is more costly. It is often reserved as a problem-solving tool when CT findings are equivocal or if there is a high clinical suspicion of recurrence despite a negative CT scan, rather than for routine first-line surveillance.

The recommended CT study carries a relative radiation level of ☢☢☢ (1-10 mSv), a moderate dose that must be considered in the context of cumulative exposure over a patient’s lifetime of surveillance. Once you’ve decided on this study, our protocol guide covers the technical details. While the guide covers a combined Chest/Abdomen/Pelvis scan, the principles for the abdomen and pelvis portion are directly applicable: CT Chest/Abdomen/Pelvis with IV Contrast.

What’s Next After CT Abdomen and Pelvis with IV Contrast? Downstream Workflow

The results of the surveillance CT will guide the subsequent clinical pathway. The goal is to act decisively on positive findings while avoiding unnecessary interventions for negative or benign results.

If the CT is positive for suspected recurrence:
The next step is typically to obtain pathologic confirmation. This may involve a CT- or ultrasound-guided biopsy of a suspicious liver lesion, peritoneal nodule, or enlarged lymph node. If the suspected recurrence is at the surgical anastomosis, an upper endoscopy with biopsy may be more appropriate. The case should be discussed at a multidisciplinary tumor board to determine the best course of action, which could include salvage chemotherapy, radiation, or targeted therapy.

If the CT is negative:
An unequivocally negative scan is reassuring. The patient can continue with their established surveillance schedule. No further immediate action is needed, and the patient should be scheduled for their next follow-up appointment and imaging study per institutional or national guidelines.

If the CT is indeterminate:
Indeterminate findings, such as a new but non-specific small liver lesion or subtle thickening near the anastomosis, present a clinical challenge. The downstream workflow may involve one of several options. A short-interval follow-up CT in 3-6 months can assess for stability or growth. Alternatively, a more sensitive imaging modality, such as the “May be appropriate” FDG-PET/CT, can be used to characterize the finding’s metabolic activity and clarify whether it represents recurrence.

Pitfalls to Avoid (and When to Get Help)

Several common pitfalls can compromise the effectiveness of gastric cancer surveillance:

  • Omitting IV Contrast: Ordering a non-contrast CT significantly limits its diagnostic utility for detecting metastases in the liver, peritoneum, and lymph nodes. Always specify “with IV contrast” unless there is a strong contraindication.
  • Ignoring Prior Scans: Surveillance imaging is fundamentally about change over time. Always ensure the interpreting radiologist has access to previous scans for comparison. A subtle new finding may be insignificant, but subtle growth of a pre-existing finding is highly concerning.
  • Misinterpreting Post-Surgical Anatomy: Normal post-operative changes can be complex. If the report is ambiguous or doesn’t align with your clinical suspicion, a direct conversation with the radiologist can provide crucial clarification.
  • Inconsistent Follow-Up Intervals: Adhering to a consistent, evidence-based surveillance schedule is key. Sporadic or delayed imaging can lead to missing the window for detecting early, treatable recurrence.

If a CT scan shows clear evidence of widespread, multi-compartment recurrence, escalation to a multidisciplinary tumor board review is the immediate next step before proceeding with invasive procedures.

Related ACR Topics and Tools

This article focuses on a single clinical scenario. For a comprehensive overview of all variants related to imaging gastric cancer, from initial diagnosis to post-treatment follow-up, please consult our parent topic hub article. It provides a breadth of information that complements this deep-dive workflow.

Frequently Asked Questions

How often should surveillance CT scans be performed for gastric cancer?

The optimal frequency and duration of surveillance imaging are not universally standardized and can vary based on the initial tumor stage, treatment received, and specific guidelines from organizations like the NCCN. Generally, surveillance is more frequent in the first 2-3 years post-treatment, when recurrence risk is highest, and may then be spaced out. Always consult current clinical practice guidelines for specific recommendations.

Why isn’t MRI routinely recommended for gastric cancer surveillance?

According to the ACR, MRI is ‘Usually not appropriate’ for this specific scenario. While it avoids ionizing radiation, CT is faster, more widely available, less expensive, and generally provides sufficient diagnostic information to detect the common patterns of recurrence. MRI is typically reserved for specific indications, like characterizing an indeterminate liver lesion found on CT, rather than for routine screening.

In which situations should I consider ordering an FDG-PET/CT for surveillance?

FDG-PET/CT is rated ‘May be appropriate’ and is best used as a second-line or problem-solving tool. Consider ordering it when a conventional CT scan is indeterminate or negative, but there is a high clinical suspicion of recurrence (e.g., rising tumor markers). It is not recommended for routine first-line surveillance due to its higher radiation dose and cost.

Is oral contrast necessary for a surveillance CT scan for gastric cancer?

The need for oral contrast depends on the specific clinical question and institutional protocol. It can be helpful for delineating the bowel loops and identifying the gastric remnant or anastomosis. However, for detecting the most common forms of recurrence (liver metastases, peritoneal nodules), IV contrast is the critical component. Many modern protocols rely on neutral oral contrast agents (like water) rather than positive (barium-based) agents.

What should I order if my patient has a severe contrast allergy or significant renal insufficiency?

If a patient cannot receive iodinated IV contrast, the standard CT is suboptimal. A non-contrast CT may be performed, but its sensitivity is much lower. In this situation, an alternative modality like an MRI of the abdomen and pelvis with and without a gadolinium-based contrast agent (if renal function permits) might be considered, despite its ‘Usually not appropriate’ rating for routine cases. An FDG-PET/CT is another option. This represents a deviation from the standard workflow and often warrants a consultation with a radiologist to determine the best alternative.

Reviewed by Pouyan Golshani, MD, Interventional Radiologist — May 30, 2026