Clinical implications of initial FDG-PET/CT in locally advanced rectal cancer treated with neoadjuvant chemoradiotherapy

Purpose: The present study evaluated the predictive and prognostic impact of initial fluorine-18-fluorodeoxyglucose-positron emission tomography/computed tomography (FDG-PET/CT) in patients with locally advanced rectal cancer treated with neoadjuvant concurrent chemoradiotherapy (CCRT). Methods: Eighty-one consecutive patients with locally advanced rectal cancer (cT3-T4 N-/N+) treated with neoadjuvant CCRT were enrolled. The FDG-PET/CT parameters, including the SUVmax, metabolic tumor volume (MTV, 50 % of SUVmax), and multiplication of the SUVmean and MTV (total lesion glycolysis, TLG), were analyzed in relation to the pathologic response and disease recurrence. Results: Five patients (6.2 %) achieved a pathologic complete response (pCR) after CCRT followed by surgery. None of the FDG-PET/CT parameters was identified as a predictive factor for pCR. After a median follow-up period of 26.7 (range 10.9-63.3) months, 19 patients (23.5 %) presented a local and/or distant recurrence. In a multivariate analysis including the clinicopathologic parameters, the TLG of the primary tumor was associated with a worse disease-free survival after neoadjuvant CCRT (HR 20.035, 95 % CI 1.726-232.559; P = 00.017). Conclusions: The TLG of the primary tumor in the initial FDG-PET/CT can be considered as a prognostic factor for patients with locally advanced rectal cancer treated with neoadjuvant CCRT.