Journal
JOURNAL OF NUCLEAR MEDICINE
Volume 60, Issue 11, Pages 1560-1568Publisher
SOC NUCLEAR MEDICINE INC
DOI: 10.2967/jnumed.118.222604
Keywords
F-18-FDG PET/CT; rectal cancer; chemoradiotherapy; bevacizumab; TLG
Funding
- Italian Ministry of Health [RF-2009-1539464, RF-2011-02346914]
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There is an unmet need for predictive biomarkers of the clinical benefit of antiangiogenic drugs. The aim of the present study was to prospectively evaluate the value of F-18-FDG PET/CT performed during and after preoperative chemoradiotherapy with bevacizumab for the prediction of complete pathologic tumor regression and survival in patients with MRI-defined high-risk locally advanced rectal cancer. Methods: Sixty-one patients treated in a nonrandomized phase II study (BRANCH) with concomitant or sequential (4 d before chemoradiotherapy) administration of bevacizumab with preoperative chemoradiotherapy were included. F-18-FDG PET/CT was performed at baseline, 11 d after the beginning of chemoradiotherapy (early), and before surgery (late). Metabolic changes were compared with pathologic complete tumor regression (TRG1) versus incomplete tumor regression (TRG2-TRG5), progression-free survival, cancer-specific survival, and overall survival. Receiver-operating-characteristic curves were calculated for those F-18-FDG PET/CT parameters that significantly correlated with TRG1. Results: Early total-lesion glycolysis and its percentage change compared with baseline (DTLG-early) could discriminate TRG1 from TRG2-TRG5. Only receiver-operating-characteristic analysis of DTLG-early showed an area under the curve greater than 0.7 (0.76), with an optimal cutoff at 59.5% (80% sensitivity, 71.4% specificity), for identifying TRG1. Late metabolic assessment could not discriminate between the 2 groups. After a median follow-up of 98 mo (range, 77-132 mo), metabolic responders (DTLG-early $59.5%) demonstrated a significantly higher 10-y progression-free survival (89.3% vs. 63.6%, P = 0.02) and cancer-specific survival (92.9% vs. 72.6%, P = 0.04) than incomplete metabolic responders. Conclusion: Our results suggest that early metabolic response can act as a surrogate marker of the benefit of antiangiogenic therapy. The findings provide further support for the use of early F-18-FDG PET/CT evaluation to predict pathologic response and survival in the preoperative treatment of patients with locally advanced rectal cancer. Delta TLG-early showed the best accuracy in predicting tumor regression and may be particularly useful in guiding treatmentmodifying decisions during preoperative chemoradiotherapy based on expected response.
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