Role of ¹⁸F-FDG PET/CT in Posttreatment Evaluation of Anal Carcinoma

Abstract

The aim of this study was to evaluate the relevance of PET/CT and F-FDG as a strategy for response evaluation after chemoradiotherapy for anal cancer. For this, the performance of posttreatmentF-FDG PET/CT, the impact on patient care, and the predictive value of metabolic response were assessed. This was a retrospective and multicenter analysis of 87 patients treated by chemoradiotherapy for anal squamous cell carcinoma between October 2007 and October 2013. All patients underwent systematic posttreatmentF-FDG PET/CT and were followed with at least a clinical examination every 4 mo for 2 y and every 6 mo thereafter. Disease progression was confirmed by biopsy for all patients in the case of local recurrence before surgery. Kaplan-Meier and Cox regression models were used to test for associations between metabolic or clinical endpoints and progression-free survival (PFS) or cause-specific survival (CSS). The median follow-up was 25 mo.F-FDG PET/CT was performed 1-8 mo (median, 4 mo) after completion of chemoradiotherapy. Overall, 25 patients relapsed and 13 died. The posttherapy F-FDG PET/CT did not show any abnormalF-FDG uptake (complete metabolic response [CMR]) in 55 patients whereas 32 displayed incomplete response (non-CMR): 15 patients with partial response and 17 with disease progression. The sensitivity of F-FDG PET/CT to detect residual tumor tissue was 92% (95% confidence interval [CI], 75%-97%), specificity was 85% (95% CI, 75%-92%), positive predictive value was 72% (95% CI, 61%-90%), and negative predictive value was 96.4% (95% CI, 90%-98.7%). The 2-y PFS was 96% (95% CI, 90-100) for patients with CMR and 28% (95% CI, 14-47) for non-CMR patients ( < 0.0001). The 2-y CSS was 100% for patients with CMR and 59% (95% CI, 42-84) for those without CMR ( < 0.0001). F-FDG PET/CT changed patient management in 14 cases (16%), with relevant modifications in 12 (14%). A Cox proportional hazards model of survival outcome indicated that a CMR was the only significant predictor of PFS and CSS ( < 0.0001). F-FDG PET/CT shows good accuracy in posttreatment evaluation of anal cancer and has a relevant impact on patient management. Moreover, CMR is associated with good survival outcome. Thus,F-FDG PET/CT may play a significant role during posttreatment follow-up of anal cancer.

Prognostic Significance of Fluorine-18 Fluorodeoxyglucose Positron Emission Tomography in Anal Squamous Cell Carcinoma: A Systematic Review and a Meta-Analysis

“…18 F-FDG-PET may aid in tailoring treatment in patients with anal SCC based on data in the pretreatment and posttreatment settings, providing independently useful clinical information and improving the selection of patients who may benefit from more aggressive treatment [14, 18, 20, 21].…”

“…Our meta-analysis demonstrated that metabolic response to therapy and preoperative SUVmax are relevant prognostic factors in patients with anal SCC; therefore, anal SCC patients with inadequate metabolic response to therapy and higher preoperative SUVmax of the anal tumor have a poorer prognosis and they could beneficiate from a more aggressive treatment (such as adequate inguinal irradiation or chemotherapy dose escalation or intensification) that cannot be routinely performed due to the expected increased toxicity [14, 18, 20, 21].…”

FDG-PET parameters predict for recurrence in anal cancer – results from a prospective, multicentre clinical trial

“…The timing of post treatment PET imaging in the published retrospective studies ranged from 0.9–5.4 months [5], 2-7 months [6], 1-8 months [7], 1-8 months [8], and 1-6 months [9]. This significantly undermines the ability to draw robust conclusions from their data and limits its application to clinical practice.…”

HYPHYCA: a prospective study in 613 patients conducting a comprehensive analysis for predictive factors of physiological 18F-FDG anal uptake

“…18 F-Fluorodeoxyglucose ( 18 F-FDG) positron emission tomography (PET) has been increasingly evaluated in the management of anal cancer patients, particularly for the initial staging of the disease and the evaluation of the therapeutic response after radiochemotherapy. In this context of post-treatment evaluation, thanks to its good negative predictive value with reported values superior to 90%, 18 F-FDG PET can avoid biopsies in case of a complete metabolic response [3][4][5]. This is clinically relevant as post radiotherapy biopsies can lead to necrosis and potentially complicated and delayed surgery.…”

“…This is clinically relevant as post radiotherapy biopsies can lead to necrosis and potentially complicated and delayed surgery. However, several authors reported the risk of local falsepositive PET [6,7], leading to low specificity and positive predictive values [4]. For example, in the Nguyen et al study [7], 5 patients were classified in partial metabolic response, but after biopsy, 3 of them were in fact in complete local response.…”