How often should PET scans be performed after completion of treatment and achievement of complete response for Non-Hodgkin Lymphoma (NHL) Diffuse Large B-Cell Lymphoma (DLBCL)?

PET/CT Surveillance After Complete Response in DLBCL Lymphoma

Routine surveillance with PET/CT scans is not recommended after achieving complete response in DLBCL lymphoma patients. 1

Recommended Follow-up Schedule

Clinical Evaluation

• History and physical examination every 3 months for 1 year, every 6 months for 2 more years, and then once a year with attention to development of secondary tumors or other long-term side effects of chemotherapy 1
• Focus on symptoms or signs that might indicate relapse 1

Laboratory Testing

• Blood count and LDH at 3,6,12, and 24 months after treatment 1
• After 24 months, laboratory tests only as needed for evaluation of suspicious symptoms or clinical findings in patients suitable for further therapy 1

Imaging

• CT scans (not PET/CT) at 6,12, and 24 months after end of treatment 1
• No routine surveillance imaging after 24 months unless clinically indicated 1

Evidence Against Routine PET/CT Surveillance

• Multiple guidelines explicitly state that routine surveillance with PET scan is not recommended 1
• Limited role for surveillance PET-CT in patients with DLBCL in complete metabolic remission 2
• No definitive evidence that routine imaging in patients in complete remission provides any outcome advantage 1
• Routine surveillance with PET may increase the incidence of secondary malignancies due to radiation exposure 1

Special Considerations

High-Risk Patients

• High-risk patients with curative options may potentially require more frequent controls 1
• Patients with high-risk IPI scores (≥3) might benefit from more vigilant surveillance in the first 18 months after treatment 2

Suspected Relapse

• If relapse is suspected based on symptoms or clinical findings, PET/CT can be performed 1
• Histological verification should be obtained whenever possible if relapse is suspected 1

Relapse Patterns

• Most relapses occur within the first two years after treatment completion 2
• Subclinical relapses detected by imaging typically occur within the first 18 months 2

• 30% of DLBCL will ultimately relapse, with an estimated incidence in the European Union of around 1/100,000/year 1

Pitfalls and Caveats

• False positive PET/CT results are common and may lead to unnecessary biopsies or treatments 2, 3
• If PET/CT is positive during follow-up, histological confirmation is strongly recommended before changing treatment 1
• The value of PET/CT is limited in indolent lymphomas due to higher rates of false positives 3
• Patients who are event-free at 2 years have an overall survival identical to the general population, emphasizing the need to only specifically monitor the disease in the early period 1

In conclusion, while PET/CT is valuable for initial staging and end-of-treatment response assessment in DLBCL, its routine use for surveillance after complete response is not supported by current evidence and guidelines. CT scans at 6,12, and 24 months, along with regular clinical evaluations and laboratory tests, provide adequate follow-up for most patients.