What is the next step in management for a patient with a history of ovarian cancer and diffuse increased FDG activity in the stomach on PET/CT?

Management of Diffuse Increased FDG Activity in the Stomach on PET/CT in a Patient with History of Ovarian Cancer

Upper endoscopy with biopsy is the recommended next step for evaluating diffuse increased FDG activity in the stomach with corresponding ill-defined thickening on PET/CT in a patient with history of ovarian cancer. 1

Rationale for Endoscopic Evaluation

The finding of diffuse increased FDG activity in the stomach with corresponding thickening on PET/CT requires thorough investigation, particularly in a patient with history of ovarian cancer. This pattern could represent:

• Metastatic disease to the stomach
• Primary gastric malignancy
• Inflammatory conditions of the stomach
• Physiologic uptake

Imaging Findings and Their Significance

The PET/CT findings of "diffuse increased FDG activity in the stomach corresponding to ill-defined diffuse thickening" are concerning for potential malignancy. According to the ACR Appropriateness Criteria, features concerning for gastric malignancy include:

• Nodular or irregular wall thickening
• Abnormal enhancement patterns
• Soft tissue attenuation of wall thickening (rather than low attenuation due to edema) 1

Diagnostic Algorithm

1. First step: Upper endoscopy with biopsy

   • Direct visualization of the gastric mucosa
   • Targeted biopsies of abnormal areas
   • Definitive histopathologic diagnosis

2. If endoscopy is negative or inconclusive:

   • Consider dedicated contrast-enhanced CT of the abdomen and pelvis with neutral oral contrast
   • MRI abdomen may be considered as a problem-solving tool

3. If malignancy is confirmed:

   • Determine if it represents:
     • Metastatic ovarian cancer (more likely given patient history)
     • Primary gastric malignancy (second primary)

Importance of Proper Evaluation

FDG-PET/CT is a valuable tool in detecting recurrent ovarian cancer, with reported sensitivity ranging from 88.2% to 95.5% and specificity from 71.4% to 93.3% 2, 3. However, it's important to note that:

• FDG uptake is not specific for malignancy
• Inflammatory conditions can cause false-positive results
• Histologic confirmation is necessary before treatment decisions

Role of PET/CT in Ovarian Cancer Follow-up

The ACR Appropriateness Criteria states that FDG-PET/CT is particularly useful when CT is indeterminate with persistent clinical concern for recurrence 1. In this case, while the most recent CT CAP was negative, the PET/CT showed concerning findings that warrant further investigation.

FDG-PET/CT has been shown to change management in up to 51.6% of patients with suspected ovarian cancer recurrence 3, making proper follow-up of positive findings essential.

Pitfalls to Avoid

1. Don't assume all FDG-avid lesions represent metastatic disease - Physiologic uptake in the stomach can occur, and primary gastric malignancies must be considered

2. Don't rely solely on imaging - Histologic confirmation is necessary before initiating treatment

3. Don't delay evaluation - Prompt investigation of PET-positive findings is important for early detection of recurrence, which may impact treatment options and outcomes

4. Don't overlook the possibility of treatment-related changes - Previous treatments can cause inflammatory changes that may appear FDG-avid

By following this approach, you can determine the nature of the gastric findings and develop an appropriate management plan for this patient with history of ovarian cancer.