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 18 F-FDG-PET/CT performed during and after preoperative chemoradiotherapy with bevacizumab for the prediction of complete pathologic tumor regression and survival in magnetic resonance imaging (MRI)-defined high-risk locally advanced rectal cancer (LARC) patients. Methods Sixty-one patients treated in a non-randomized phase II study (BRANCH) with concomitant or sequential (4 days before chemoradiotherapy) administration of bevacizumab with preoperative chemoradiotherapy were included. 18 F-FDG PET/CT was performed at baseline, 11 days after the beginning of chemoradiotherapy (early) and before surgery (late). Metabolic changes were compared with pathological complete (TRG1) vs incomplete (TRG2-5) tumor regression, progression-free survival (PFS), cancer specific survival (CSS) and overall survival (OS). Receiver operating characteristic (ROC) curves were calculated for those 18 F-FDG-PET/CT parameters that significantly correlated with TRG1. Results Early total lesion glycolysis (TLG-early) and its percent change compared to baseline (ΔTLG-early) could discriminate TRG1 from TRG2-5. Only ROC analysis of ΔTLG-early showed an area under curve (AUC) > 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 two groups. After a median follow-up of 98 months (range 77-132) metabolic responders (ΔTLG-early ≥ 59.5%) demonstrated a significantly higher 10-year PFS (89.3% vs 63.6%, p=0.02) and CSS (92.9% vs 72.6%, p=0.04) compared to incomplete metabolic responders. Conclusion Our results suggest that early metabolic response can act as a surrogate marker of the benefit of antiangiogenic therapy and provide further support for the use of early 18 F-FDG-PET/CT evaluation to predict pathological response and survival in the preoperative treatment of patients with LARC. ΔTLG-early showed the best accuracy in predicting TRG and may be particularly useful in guiding treatment modifying decisions during preoperative chemoradiotherapy based on expected response.
Preoperative Radiochemotherapy with Bevacizumab in High RiskLocally Advanced F-FDG PET/CT Is an Early Predictor of Pathologic Tumor Response and Survival to 18 http://jnm.snmjournals.org/content/early/2019/03/14/jnumed.118.222604 This article and updated information are available at: http://jnm.snmjournals.org/site/subscriptions/online.xhtml Information about subscriptions to JNM can be found at: http://jnm.snmjournals.org/site/misc/permission.xhtml