18F-FDG PET/CT for first follow-up post chemotherapy in lymphoma: Is it mandatory to do whole body scan?

Objective: To assess the feasibility of 18F-2-fluoro-2-deoxy-D-glucose positron emission tomography/computed tomography (FDG-PET/CT) scan limited to the original sites of lymphoma in 1st follow-up (F/U) post-chemotherapy to reduce patient’s radiation exposure and scan time. Patients and methods: FDG PET/CT scans of 100 lymphoma patients were reviewed and the sites of disease in pre-Chemotherapy and the 1st F/U post-chemotherapy scans were recorded. The supposed saved time from PET part of the scan and reduction in radiation dose from CT part if PET/CT scan limited to the original sites of lymphoma in 1st F/U post-chemotherapy scan is used, were calculated. Result: 45% of 1st F/U post-chemotherapy PET/CT scans showed no significant residual FDG-uptake indicating complete metabolic response. Significant residual FDG-uptake at known disease sites was seen in 55% of 1st F/U post-chemotherapy scans indicating residual disease. No lesions with significant FDG uptake in new sites were detected in the 1st F/U post-chemotherapy PET/CT indicating no unexpected sites of lymphoma. The supposed reduction in the mean scan time and radiation dose is 5.3 ± 1.47 minutes and 4.2 ± 1.2 mSv respectively if scan limited to the sites of known disease is used in 1st FU-P-CHT, without missing any significant findings. Conclusion: It is not mandatory to do WB 18F-FDG PET/CT scan in assessment of early response to chemotherapy in curable lymphoma and it may be sufficient to limit scans to the sites of known disease without missing any significant findings, resulting in significant reduction in total radiation dose and time saving.