What is the preferred method of follow-up imaging for a patient with a history of non-Hodgkin's lymphoma (NHL), computed tomography (CT) scan or ultrasound?

CT Scans Are Preferred Over Ultrasound for Follow-up Imaging in Non-Hodgkin Lymphoma

CT scans should be used for follow-up imaging in patients with a history of non-Hodgkin lymphoma (NHL), but only when clinically indicated by symptoms, abnormal physical findings, or concerning laboratory results rather than as routine surveillance. 1

Imaging Recommendations for NHL Follow-up

Preferred Imaging Modality

• CT is the preferred imaging modality for follow-up in NHL patients when imaging is clinically indicated
• PET-CT is recommended for FDG-avid lymphoma subtypes when relapse is suspected 1
• Ultrasound has limited utility and is not recommended as the primary follow-up imaging modality 1

When to Perform Follow-up Imaging

• Routine surveillance imaging is strongly discouraged by current guidelines 1, 2
• Imaging should be performed only when clinically indicated:
  • New or worsening symptoms
  • Abnormal physical examination findings
  • Concerning laboratory results (e.g., elevated LDH)
  • Suspected relapse based on clinical assessment 1, 2

Special Considerations

• For indolent lymphomas with residual intra-abdominal or retroperitoneal disease after therapy, judicious use of CT scans can be considered 1
• In aggressive NHL subtypes (like DLBCL), CT has been shown to detect only 22% of relapses, with most relapses (78%) detected through symptoms, physical examination, or laboratory abnormalities 3

Clinical Follow-up Schedule

For Curable NHL Histologies (e.g., DLBCL)

• Clinical evaluations every 3 months during the first 2 years
• Every 6 months for the next 3 years
• Then annually thereafter 1, 2

For Incurable NHL Histologies (e.g., follicular lymphoma)

• Clinical evaluations every 3-6 months
• Frequency determined by pretreatment risk factors and treatment response 1, 2

Laboratory Monitoring

• Complete blood count (CBC)
• Metabolic panel
• Serum lactate dehydrogenase (LDH) 1, 2

Evidence Quality and Considerations

The recommendation against routine surveillance imaging is based on high-quality evidence showing:

• Routine surveillance CT detects only a small percentage of asymptomatic relapses (22%) 3
• No survival benefit has been demonstrated for asymptomatic relapse detection via routine imaging 3, 4
• Unnecessary radiation exposure increases the risk of second malignancies 4
• False-positive rates with PET scans exceed 20%, leading to unnecessary investigations, biopsies, expense, and patient anxiety 1

Common Pitfalls to Avoid

• Performing routine surveillance imaging without clinical indications
• Relying on ultrasound as the primary follow-up imaging modality
• Neglecting regular clinical evaluations and laboratory monitoring
• Failing to consider the specific NHL subtype when determining follow-up approach
• Exposing patients to unnecessary radiation through excessive imaging

When imaging is clinically indicated for suspected relapse, CT is the preferred modality over ultrasound due to its superior sensitivity and ability to comprehensively evaluate nodal and extranodal sites throughout the body.