Accuracy of radiological staging in identifying high-risk colon cancer patients suitable for neoadjuvant chemotherapy: a multicentre experience.

Aim:  A pilot study was undertaken to determine the accuracy of CT staging in identifying patients with high risk colon cancers who would be considered a candidates for a neoadjuvant therapy trial (FOxTROT) and those at low risk (T1/T2) who would be excluded.. Method:  Participating radiologists from 19 centres attended workshops for standardisation of image interpretation according to previously defined prognostic criteria: good prognosis tumoursd including, T1/T2, intermediate prognosis, T3 <5mm tumour invasion beyond the muscularis propria (MP) and poor prognosis tumours including T3 with tumour extension ≥ 5mm beyond the MP or T4). The CT findings were compared with histopathology as the reference standard. Results:  Of 94 patients with radiological and pathological data, 71% were categorised by CT as having a poor prognosis. The sensitivity and specificity of CT in identifying these were 87% (95%CI: 74%-94%) and 49% (95%CI: 33%-65%). Sensitivity and specificity for tumour infiltration beyond the MP (T3/T4 vs T1/T2) was 95% (95%CI: 87% - 98%) and 50% (95%CI: 22%- 77%) respectively. Including all CT staged T3 and T4 patients in the trial, would have increased the proportion eligible for entry to 89% (n=84) without affecting the false positive rate of 7%. Some 20% of T3/T4 patients would, have been ineligible for FOxTROT because of synchronous metastases. Conclusion:  In a multicentre setting, CT scanning identified high risk (T3/4) colon cancers with minimal overstaging of T1/T2 tumours, thus establishing the feasibility of radiologically-guided neoadjuvant chemotherapy.