Recent chemotherapy reduces the maximum-standardized uptake value of 18F-fluoro-deoxyglucose positron emission tomography in colorectal cancer.

Background/aims: The aim of this study was to evaluate the influence of recent chemotherapy on the patterns of the maximum-standardized uptake value (M-SUV) and sensitivity of (18)F-fluoro-deoxyglucose positron emission tomography/computed tomography ((18)F-FDG-PET/CT) in colorectal cancer.
Methods: We retrospectively analyzed the FDG-PET/CT of 509 patients who underwent surgery for colorectal cancer. Subgroup analysis was performed according to chemotherapy status; 401 patients were not treated with chemotherapy and 108 patients were treated with chemotherapy within 6 months prior to surgery. Pathologic analysis of the surgical specimen was used as the gold standard.
Results: The M-SUV was significantly lower in patients treated with chemotherapy than in those not treated with chemotherapy in pathologically confirmed same stages of disease. The difference in the sensitivity of the M-SUV according to chemotherapy status was greatest using a cutoff M-SUV value of 6.4 (p<0.001). The longest diameter of the primary tumor was the most important factor that correlated with M-SUV of the primary tumor irrespective of the chemotherapy effect (p<0.001). The M-SUV of the primary tumor was not an independent predictor of lymph node metastasis in colorectal cancer.
Conclusions: The results indicate that the M-SUV of FDG-PET/CT should be interpreted in the context of concurrent chemotherapy.