Diagnostic accuracy and treatment benefit of PET/CT in staging of colorectal cancer compared to conventional imaging

BACKGROUND: Until recently the use of positron emission tomography (PET) CT for staging in colorectal cancer (CRC) has been limited to the detection of distant metastasis in advanced disease. But with the introduction of neoadjuvant treatments in CRC, accurate pre-treatment staging has become more relevant. AIMS: The aim of the study was to assess the staging accuracy for nodal and distant metastasis of PET/CT compared to computed tomography (CT) alone in CRC. Secondary endpoints were overall survival (OS) and cost of CT compared to PET/CT. METHODS: A retrospective analysis of 539 cases with CRC staged with PET/CT and or CT between 2015 and 2021 in a Swiss tertiary referral center was performed. In 471 patients for nodal staging and 479 for staging of distant metastasis the clinical stage of both modalities was compared with pathological stage. RESULTS: The distribution of UICC stages (n = 479) was as follows: Stage I 62 cases (12.9 %), Stage II 127 cases (26.5 %), Stage III 199 cases (41.5 %), Stage IV 91 cases (19.0 %). CT alone compared to PET was able to predict nodal involvement with a sensitivity of 55.2 % (95%CI 5.7-59.7 %) and 66.7 % (95%CI 62.4-70.9 %), respectively. The specificity was 67.0 % (95%CI 62.8-71.3 %) for CT and 63.6 % (95%CI 59.3-68.0 %) for PET. The positive predictive value was 49.5 % for CT vs. 51.8 % for PET. The sensitivity of metastasis detection was 53.6 % (95%CI 49.1-58.1 %) for CT and 82.5 % (95%CI 79.1-85.9 %) for PET. CONCLUSIONS: PET/CT showed higher sensitivity in the detection of lymph node involvement and metastases in CRC patients compared to CT alone.