Comparison of Diagnostic Performance of Whole-Body 360° CZT Bone SPECT/CT and Planar Bone Scintigraphy in Detecting Bone Metastasis in Small Cell Lung Cancer.

Background/Objectives: We aimed to compare the diagnostic performances of planar bone scintigraphy and whole-body 360° cadmium-zinc-telluride (CZT) bone single-photon emission computed tomography/computed tomography (SPECT/CT) in detecting bone metastasis in patients with small cell lung cancer (SCLC). Methods: We retrospectively evaluated two separate, non-randomized cohorts of 175 patients with SCLC who underwent staging bone scintigraphy, comprising 93 and 82 patients who underwent planar bone scintigraphy using a conventional dual-head gamma camera and whole-body bone SPECT/CT using a full-ring 360° CZT camera, respectively. Both imaging examinations were visually assessed and compared using patient- and lesion-based analyses of their diagnostic performances. Results: Whole-body bone SPECT/CT showed fewer equivocal findings and almost perfect inter-reader agreement. On the patient-based analysis, whole-body bone SPECT/CT demonstrated higher unadjusted observed diagnostic accuracy than planar bone scintigraphy (87.8% vs. 73.1%; p = 0.016), with higher observed sensitivity (79.2% vs. 53.3%), specificity (91.4% vs. 82.5%), positive predictive value (79.2% vs. 59.3%) and negative predictive value (91.4% vs. 78.8%). However, on a lesion-based analysis, whole-body bone SPECT/CT exhibited a low sensitivity of 47.5%, with particularly low detection rates for spine and pelvic metastases (29.4%), despite showing higher observed sensitivity than planar bone scintigraphy (20.1%). Conclusions: In two separate retrospective cohorts of SCLC patients, whole-body bone SPECT/CT showed higher unadjusted observed patients-based diagnostic performance than planar bone scintigraphy. However, its lesion-level sensitivity remained low, particularly in the spine and pelvis.