Gallium-68 perfusion positron emission tomography/computed tomography to assess pulmonary function in lung cancer...

Pre-operative evaluation of lung cancer patients relies on calculation of predicted post-operative (PPO) lung function based on split lung function testing. Pulmonary perfusion (Q) PET/CT can now be performed by substituting Technetium-99 m labeling of macroaggregated albumin (MAA) with Gallium-68. This study compares Q PET/CT with current recommended methods of pre-operative lung function assessment.

Twenty-two patients planned for curative surgical resection (mean FEV1 77 %, SD 21 %; mean DLCO 66 %, SD 17 % predicted) underwent pre-operative Q PET/CT. Sixteen patients also underwent conventional lung scintigraphy. Lobar and lung split PPO lung function were calculated using Q PET/CT and current recommended methods, i.e. calculation based on anatomical segments for lobar function, and conventional perfusion scan for pneumonectomy. Bland-Altman statistics were used to calculate agreement between methods for PPO FEV1 and PPO DLCO.

While mean split lobar functions were comparable, there was variation on an individual level between Q PET/CT and the anatomical method, with absolute difference over 5 % and 10 % in 37 % and 11 % of patients, respectively. For lobectomy the mean difference in PPO FEV1 was-1.2, but limits of agreement were-10 to 8.1 %. For DLCO, values were-1.1 % and-9.7 to 7.5 %, respectively. For pneumonectomy, PPO FEV1 values were-0.4 and-5.9 to 5.1 %. For DLCO, values were 0.3 % and-5.1 to 4.6 %.

While anatomic estimation provides "fixed" results, split lobar functions computed with Q PET/CT vary widely, reflecting the intra and inter-individual variability of regional lung function. Further studies to assess the role of Q PET/CT in predicting peri-operative risk in lung cancer patients planned for lobectomy are warranted.