Diagnostic performance of ¹⁸F-FDG PET-CT and SPECT for bone metastases from colorectal cancer: a retrospective study

To compare the diagnostic performance of 18F-FDG PET-CT and SPECT whole-body bone imaging for detecting bone metastases in patients with colorectal cancer.

A retrospective analysis was performed on 118 patients with pathologically confirmed colorectal cancer who underwent both 18F-FDG PET-CT and SPECT whole-body bone imaging within one month during follow-up for newly suspected bone metastases. The cohort included 62 males and 56 females, with a mean age of 59.1 ± 7.6 years. The final diagnosis of bone metastases was established based on comprehensive imaging follow-up, including CT, MRI, SPECT, PET-CT, and clinical progression over more than 6 months. Diagnostic performance was evaluated on a lesion-based basis.

A total of 533 abnormal lesions were detected in 118 patients, including 469 metastatic lesions and 64 benign lesions. PET-CT detected 423 lesions, whereas SPECT detected 398 lesions, with 288 lesions identified by both modalities. PET-CT correctly identified 428 metastatic lesions, yielding a sensitivity of 91.3%, while SPECT identified 280 metastatic lesions, with a sensitivity of 59.7%. Among the benign lesions, PET-CT correctly identified 60 lesions, resulting in a specificity of 93.8%, whereas SPECT correctly identified 30 lesions, with a specificity of 46.9%. The overall diagnostic accuracy of PET-CT and SPECT was 91.6% and 58.2%, respectively.

18F-FDG PET-CT demonstrated significantly higher sensitivity, specificity, and diagnostic accuracy than SPECT for detecting bone metastases from colorectal cancer. PET-CT may provide superior diagnostic value for predominantly osteolytic bone metastases in colorectal cancer, while SPECT remains an important and widely available first-line screening modality in routine clinical practice.