Effect of respiratory gated positron emission tomography on clinical staging and management of lung cancer

Objectives Positron emission tomography (PET) is an essential imaging modality for staging of primary lung cancer. However, respiratory motion artifacts during PET imaging potentially introduce diagnostic uncertainties. In this study, the effect of optimal respiratory gating on clinical disease staging of patients with primary lung cancer was investigated.

Methods From our fast-track outpatient diagnostic program, 55 lung cancer patients, who underwent respiratory gated [¹⁸F]-fluorodeoxyglucose (FDG) PET, were included. Two nuclear medicine physicians scored the number and anatomical location of the lesions, lymph node basins and presence of distant metastases in non-gated and gated images. A lymph node (N) and metastasis (M) stage was assigned according to the TNM classification 7^th revision. Up-staging from N₀ or M₀ towards any positive N (N₊) or M (M₊) and down-staging from N₊ or M₊ towards N₀ or M₀ was recorded, as this would directly affect patient management: operable N₀M₀ patients are eligible for curative resection, whilst any N₊ or M₊ would have required additional diagnostic procedures.

Results Respiratory gating resulted in detection of more lesions in 5 and 8 patients (9% and 15%) for observer 1 and 2, respectively. This did not result in any migration in T or M-stage. Migration in N-stage occurred in 4 and 6 patients (7% and 11%) for observer 1 and 2 respectively. Up-staging from N₀ to N₊ was observed in 3 and 2 patients with an M₀-stage for observers 1 and 2 respectively. Similarly, observers 1 and 2 down-staged 1 and 3 patients from N₊ to N₀ respectively. Comparison with histopathlogical data and follow-up CT imaging showed that staging accuracy was improved when respiratory gating was performed.

Conclusions Results suggests that respiratory gating can change management of patients with primary lung cancer. Respiratory gating improved staging accuracy, mainly in assessment of lymph node involvement. In up to 14% it changed N-stage and in at least 5% it would directly influence patient management.

Research Support W. Grootjans receives an educational grant from Siemens Healthcare, The Hague, The Netherlands