Background: [18F]-fluorodeoxyglucose with positron-emission tomography (PET) and computed tomography (CT) scans were used to assess morphological and metabolic tumour response after chemotherapy in metastatic colorectal cancer.
Patients and methods: Twenty-five patients were evaluated after 4 courses of chemotherapy (+/-target therapy), and among them 20 patients after 2 courses. Response Evaluation Criteria In Solid Tumors (RECIST) and European Organisazion for Research and Treatment of Cancer (EORTC) criteria were used to evaluate CT and PET respectively.
Results: Discrepancies between the two procedures were noted after 4 courses of chemotherapy in patient-based analysis. Two morphologically complete responses (CR) were correlated with metabolic response. Seven morphological partial responses (PR) were evaluated as 3 metabolic PR, 2 CR and 1 progressive disease (PD). Seventeen cases of morphologically stable disease (SD) were evaluated as 3 metabolic CR, 13 PR and 1 PD. These discrepancies were confirmed in lesion-based analysis. Perfect concordance was noted between metabolic responses obtained after 2 and 4 cycles.
Conclusion: Morphological and metabolic imaging does not permit concordant therapeutic assessment in metastatic colorectal cancer.