What is the recommended frequency of Positron Emission Tomography (PET) scans for patients with follicular lymphoma?

PET Scan Frequency Recommendations for Follicular Lymphoma

PET scans are not recommended for routine surveillance in follicular lymphoma patients and should only be performed when clinically indicated based on symptoms or abnormal findings. 1

Initial Staging and Diagnosis

• PET-CT is not routinely recommended for initial staging according to consensus guidelines 1
• However, PET-CT may be useful in specific situations:
  • To confirm localized stage I/II disease before radiotherapy 1
  • To identify areas suspected of disease transformation 1
  • As a baseline for future response assessment if treatment is planned 1

During and After Treatment

Response Assessment

• PET-CT should be used for response assessment in follicular lymphoma as it has superior predictive value compared to conventional CT 2, 3
• End-of-therapy PET has strong prognostic value:
  • Patients with negative post-induction PET have significantly better progression-free survival (63.4% vs 23.2% at 4 years) 2
  • PET-negative status is associated with better overall survival (97.1% vs 87.2% at 4 years) 2

Follow-Up and Surveillance

• Routine surveillance scans are explicitly discouraged 1
• The false-positive rate with PET scans exceeds 20%, leading to unnecessary investigations, radiation exposure, biopsies, expense, and patient anxiety 1
• Follow-up scans should be prompted by clinical indications only 1

Recommended Follow-Up Schedule

Based on guidelines, the recommended clinical follow-up (without routine imaging) is:

• Every 3 months for the first 2 years
• Every 4-6 months for the next 3 years
• Annually thereafter 1

Special Considerations

• Judicious use of follow-up scans may be considered only in patients with residual intra-abdominal or retroperitoneal disease after therapy 1
• In clinical trials with time-dependent endpoints, CT scans may be performed at study-designated intervals 1

Pitfalls to Avoid

1. Ordering routine surveillance PET scans without clinical indications
2. Overreliance on CT-based response assessment, which has weaker predictive value than PET 2, 4
3. Failure to use PET for end-of-therapy response assessment, which provides valuable prognostic information 2, 3
4. Unnecessary radiation exposure from frequent scans in a disease that often has an indolent course

PET-CT has transformed response assessment in follicular lymphoma and should replace conventional CT for this purpose 2, but its use should be strategic and clinically indicated rather than routine.