RESUMEN
PURPOSE: To prospectively evaluate the usefulness of (18)F-FDG PET/CT) imaging for predicting histopathological response and long-term clinical outcomes in locally advanced rectal cancer (LARC). METHODS: This prospective study included 38 patients with a confirmed diagnosis of LARC (cT3-4 or cN+) who underwent (18)F-FDG PET/CT before and after neoadjuvant therapy (NAT). Total mesorectal excision was scheduled 6 weeks after NAT and was followed by an expert histopathological analysis of the surgical specimen. Baseline variables and previously identified maximum FDG standardized uptake value (SUVmax) cut-off values before NAT (SUVmaxPRE ≥6) and after NAT (SUVmaxPOST ≥2), and the absolute and percentage reductions from baseline SUVmax (∆SUVmax <4 and ∆SUVmax% <65 %, respectively) were applied to differentiate patients showing a metabolic tumour response from nonresponders. These features were correlated with tumour regression grade (TRG), disease-free survival (DFS) and overall survival (OS). RESULTS: Significantly higher 5-year DFS and OS were seen in 19 responders (TRG 3 or 4) than in 19 nonresponders (TRG 0-2; 94.4 vs. 48.8 %, p = 0.001; 94.7 vs. 63.2 %, p = 0.02, respectively). In multivariate analysis the only PET/CT SUVmax-based parameter significantly correlated with the likelihood of recurrence and survival was ∆SUV% <65 % (HR = 5.95, p = 0.02, for DFS; HR = 5.26, p = 0.04, for OS) CONCLUSION: This prospective study proved that (18)F-FDG PET/CT is a valuable imaging tool for assessing rectal cancer TRG and long-term prognosis, and could potentially serve as an intermediate endpoint in treatment optimization research and rectal cancer patient care.
Asunto(s)
Fluorodesoxiglucosa F18 , Imagen Multimodal , Tomografía de Emisión de Positrones , Neoplasias del Recto/diagnóstico por imagen , Neoplasias del Recto/terapia , Tomografía Computarizada por Rayos X , Adulto , Anciano , Femenino , Estudios de Seguimiento , Humanos , Masculino , Persona de Mediana Edad , Pronóstico , Estudios Prospectivos , Neoplasias del Recto/metabolismo , Neoplasias del Recto/patología , Reproducibilidad de los Resultados , Factores de Tiempo , Resultado del TratamientoRESUMEN
OBJECTIVE: To evaluate efficacy of (18)F-FDG PET(CT) in the staging and re staging of patients with locally advanced rectal cancer, its potential role in predicting pathological response to neoadjuvant therapy. PATIENTS AND METHODS: Patients with confirmed diagnosis of rectal cancer (T2-4 or N+) were prospectively studied with (18)F-FDG PET before and after neoadjuvant therapy. Surgery was programmed 4-6 weeks after treatment followed by an expert histological analysis of the surgical specimen. Response to neoadjuvant treatment was assessed using two specific variables: difference in SUV (difSUV) pre/post-neoadjuvant treatment and response index (RI). RESULTS: A total of 64 patients were enrolled for pathological and bio-metabolic response assessment. Compared to cN0, cN+ patients had a higher SUV(1) mean value (6.5 vs. 7.6, p=0.04) and ypN+ patients had higher SUV(2) mean values (2.4 vs 3.5, p=0.06). difSUV values of ≥4 was the most efficient diagnostic parameter (sensitivity=45.8%, specificity=86.2%, positive predictive value (PPV)=73.3%, negative predictive value(NPV)=65.7%). With an RI of 66.6%, the sensitivity was 38.5%, specificity=81.5%, PPV=66.6%, and NPV=57.8%. Patients who experienced disease progression had an RI≤66% and a difSUV≤4. CONCLUSION: (18)F-FDG PET has proven to be an accurate diagnostic technique for assessing rectal cancer response to neoadjuvant therapy. The results in terms of sensitivity, specificity, PPV and NPV were similar, if not superior, to those reported with other diagnostic imaging techniques.