COMMENTARY

18F-FDG PET for Predicting Response in Rectal Cancer

Hossein Jadvar, MD, PhD, MPH, MBA

Disclosures

June 15, 2015

Value of 18F-FDG PET for Predicting Response to Neoadjuvant Therapy in Rectal Cancer: Systematic Review and Meta-analysis

Maffione AM, Marzola MC, Capirci C, Colletti PM, Rubello D
AJR Am J Roentgenol. 2015;204:1261-1268

Summary

The aim of this systematic review and meta-analysis[1] was to assess the predictive value of fluorodeoxyglucose (FDG) PET/CT for pathologic response to neoadjuvant chemoradiotherapy in locally advanced rectal cancer. Meta-analysis was performed on 29 studies (published up to January 2014) that incorporated a range of 21 to 73 patients per study. An additional five studies were included in a qualitative analysis incorporating a total of 1526 patients (global cohort). FDG PET/CT showed pooled sensitivity of 73% and pooled specificity of 77% in the global cohort. The pooled accuracy was similar for early PET restaging (median of 1.5 weeks after beginning of chemoradiotherapy) and posttreatment evaluation (median of 6.5 weeks after therapy completion). The pretreatment tumor maximum standardized uptake value (SUVmax) was not predictive of response to chemoradiotherapy. The authors concluded that this meta-analysis supports the use of FDG PET for restaging locally advanced rectal cancer.

Viewpoint

Systematic reviews and meta-analyses are important contributions to the relevant literature.[2] In this one, the value of FDG PET/CT for predicting response to neodjuvant chemoradiotherapy was assessed. PET is advantageous over CT and MRI in that the latter 2 imaging modalities are often limited in differentiating posttreatment fibrosis from residual or recurrent tumor. Through exclusion criteria, this review included more focused studies; however, some residual heterogeneity could not be avoided (eg, variable treatment regimen). Nevertheless, the pooled sensitivity and specificity of FDG PET/CT in this clinical setting were reasonably adequate, regardless of the specific metabolic parameter used (SUVmax, retention index, change in total lesion glycolysis, and change in metabolic tumor volume). This report will certainly contribute to the current activities to develop appropriate use criteria for FDG PET/CT in retagging cancer under the umbrella of increasing government and payer decrees for clinical practice through evidence-based medicine.

Abstract

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