Does baseline [18F] FDG-PET/CT correlate with tumor staging, response after neoadjuvant chemoradiotherapy, and prognosis in patients with rectal cancer?

Letizia Deantonio,Marco Krengli,Gianmauro Sacchetti,Angela Caroli,Daniela Ferrante,Lucia Turri,Erinda Puta,Francesco Apicella,Marco Brambilla

doi:10.1186/s13014-018-1154-3

Abstract

Background[18F] fluorodeoxyglucose positron emission tomography/computed tomography ([18F] FDG-PET/CT) may be used for tumor staging and prognosis in several tumors but its role in rectal cancer is still debated. The aim of the present study was to assess the correlation of baseline [18F] FDG-PET parameters with tumor staging, tumor response (tumor regression grade (TRG)), and outcome in a series of patients affected by locally advanced rectal cancer (LARC) treated with neoadjuvant chemoradiotherapy (CRT).MethodsOne hundred patients treated with neoadjuvant CRT and radical surgery were enrolled in the present study. Maximum standardized uptake value (SUVmax), SUVmean, metabolic tumor volume (MTV), and total lesion glycolysis (TLG) at the baseline [18F] FDG-PET were calculated. These PET parameters were correlated with tumor staging, histopathological data (TRG1 vs. TRG2–5 and TRG1–2 vs. TRG3–5), disease-free survival, and overall survival.ResultsSUVmax and SUVmean of primary tumor were statistically associated with T4-stage. SUVmax, SUVmean, and TLG did not result statistically associated with TRG (TRG1 or TRG1–2). MTV resulted statistically associated with TRG1–2 group (OR 2.9; 95% CI 1.2–7.1). Finally, no PET parameter was significantly associated with disease-free or overall survival.ConclusionOur results showed that baseline [18F] FDG-PET parameters correlated with tumor staging, and only MTV correlated with TRG 1–2. PET parameters failed to predict disease-free and overall survival after treatment completion. The results leave open to further studies the issue of identifying patients suitable for conservative approaches.

Highlights

Treatment approach to rectal cancer has greatly evolved over the past years
The SUVmax (p = 0.01), SUVmean (p = 0.01), metabolic tumor volume (MTV) (p = 0.003) and total lesion glycolysis (TLG) (p = 0.0004) values were significantly higher in the cT4 than in the cT3 cases
Primary tumors with SUVmax or SUVmean higher than median values were statistically associated with cT4-stage

Summary

Introduction

In locally advanced rectal cancer (LARC), neoadjuvant chemoradiotherapy (CRT) followed by surgical resection with total mesorectal excision is the current standard treatment approach [1, 2]. 50 to 60% of the patients can reach a down-staging following CRT with about 20% of complete pathological response [3]. This rate of pathological response has raised the issue of organ preservation. The study reported 49% of complete clinical response after CRT in a series of 183 patients with T2–4 N0–2 distal rectal tumors. The “watch and wait” strategy or the local excision after CRT has been explored as organ-preserving

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