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      The value of metabolic imaging to predict tumour response after chemoradiation in locally advanced rectal cancer

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          Abstract

          Background

          We aim to investigate the possibility of using 18F-positron emission tomography/computer tomography (PET-CT) to predict the histopathologic response in locally advanced rectal cancer (LARC) treated with preoperative chemoradiation (CRT).

          Methods

          The study included 50 patients with LARC treated with preoperative CRT. All patients were evaluated by PET-CT before and after CRT, and results were compared to histopathologic response quantified by tumour regression grade (patients with TRG 1-2 being defined as responders and patients with grade 3-5 as non-responders). Furthermore, the predictive value of metabolic imaging for pathologic complete response (ypCR) was investigated.

          Results

          Responders and non-responders showed statistically significant differences according to Mandard's criteria for maximum standardized uptake value (SUV max) before and after CRT with a specificity of 76,6% and a positive predictive value of 66,7%. Furthermore, SUV max values after CRT were able to differentiate patients with ypCR with a sensitivity of 63% and a specificity of 74,4% (positive predictive value 41,2% and negative predictive value 87,9%); This rather low sensitivity and specificity determined that PET-CT was only able to distinguish 7 cases of ypCR from a total of 11 patients.

          Conclusions

          We conclude that 18-F PET-CT performed five to seven weeks after the end of CRT can visualise functional tumour response in LARC. In contrast, metabolic imaging with 18-F PET-CT is not able to predict patients with ypCR accurately.

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          Most cited references21

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          Locally advanced rectal cancer: added value of diffusion-weighted MR imaging in the evaluation of tumor response to neoadjuvant chemo- and radiation therapy.

          To investigate the added value of diffusion-weighted (DW) magnetic resonance (MR) imaging in the evaluation of complete response (CR) to neoadjuvant combined chemotherapy and radiation therapy (CRT) in patients with locally advanced rectal cancer. Institutional review board approval was obtained for this retrospective study, and the patient informed consent requirement was waived. Forty consecutive patients with locally advanced rectal cancer (>or=T3 or lymph node positive) who underwent CRT and subsequent surgery were enrolled in this study. All patients underwent pre- and post-CRT 1.5-T rectal MR imaging and post-CRT DW MR imaging. For qualitative analysis, two radiologists who were blinded to pathologic staging and prior imaging data retrospectively and independently reviewed conventional MR images and the combined set of MR images and DW MR images over a 2-week interval and recorded their confidence level with respect to the CR to neoadjuvant CRT. Diagnostic accuracy was calculated for each reviewer with receiver operating characteristic (ROC) curve analysis. For quantitative analysis, a third radiologist measured the apparent diffusion coefficient (ADC) of the region of interest three times. Mean ADCs in the CR group were compared with those in the non-CR group. Pathology reports served as the reference standard. Diagnostic accuracy (area under the ROC curve [A(z)]) in the evaluation of CR was significantly improved after additional review of DW MR images for both reviewers: For reviewer 1, A(z) improved from 0.676 to 0.876 (P = .005), whereas for reviewer 2, A(z) improved from 0.658 to 0.815 (P = .036). Mean ADC ([1.62 +/- 0.36] x 10(-3) mm(2)/sec) (standard deviation) of the CR group (n = 11) was significantly higher than that ([1.04 +/- 0.24] x 10(-3) mm(2)/sec) of the non-CR group (n = 29) (P < .0001). Adding DW MR imaging to conventional MR imaging yields better diagnostic accuracy than use of conventional MR imaging alone in the evaluation of CR to neoadjuvant CRT in patients with locally advanced rectal cancer.
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            Monitoring and predicting response to therapy with 18F-FDG PET in colorectal cancer: a systematic review.

            Molecular imaging with (18)F-FDG PET has been proven useful in the management of colorectal cancer. (18)F-FDG PET plays a pivotal role in staging before surgical resection of recurrent colorectal cancer and metastases, in the localization of recurrence in patients with an unexplained rise in serum carcinoembryonic antigen levels, and in the assessment of residual masses after treatment. Currently, there is increasing interest in the role of (18)F-FDG PET beyond staging. The technique appears to have significant potential for the characterization of tumors and for the prediction of prognosis in the context of treatment stratification and early assessment of tumor response to therapy. This systematic review provides an overview of the literature on the value of (18)F-FDG PET for monitoring and predicting the response to therapy in colorectal cancer. The review covers chemotherapy response monitoring in advanced colorectal cancer, monitoring of the effects of local ablative therapies, and preoperative radiotherapy and multimodality treatment response evaluation in primary rectal cancer. Given the added value of (18)F-FDG PET for these indications, implementation in clinical practice and systematic inclusion in therapeutic trials to exploit the potential of (18)F-FDG PET are warranted.
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              Comparison of CT, MRI and FDG-PET in response prediction of patients with locally advanced rectal cancer after multimodal preoperative therapy: is there a benefit in using functional imaging?

              The aim of this study was to compare CT, MRI and FDG-PET in the prediction of outcome of neoadjuvant radiochemotherapy in patients with locally advanced primary rectal cancer. A total of 23 patients with T3/4 rectal cancer underwent a preoperative radiochemotherapy combined with regional hyperthermia. Staging was performed using four-slice CT (n=23), 1.5-T MRI (n=10), and (18)F-FDG-PET (n=23) before and 2-4 weeks after completion of neoadjuvant treatment. Response criteria were a change in T category and tumour volume for CT and MRI and a change in glucose uptake (standard uptake value) within the tumour for FDG-PET. Imaging results were compared with those of pretherapy endorectal ultrasound and histopathological findings. Histopathology showed a response to neoadjuvant therapy in 13 patients whereas 10 patients were classified as nonresponders. The mean SUV reduction in responders (60+/-14%) was significantly higher than in nonresponders (37+/-31%; P=0.030). The sensitivity and specificity of FDG-PET in identifying response was 100% (CT 54%, MRI 71%) and 60% (CT 80%, MRT 67%). Positive and negative predictive values were 77% (CT 78%, MRI 83%) and 100% (CT 57%, MRI 50%) (PET P=0.002, CT P=0.197, MRI P=0.500). These results suggest that FDG-PET is superior to CT and MRI in predicting response to preoperative multimodal treatment of locally advanced primary rectal cancer.
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                Author and article information

                Journal
                Radiat Oncol
                Radiation Oncology (London, England)
                BioMed Central
                1748-717X
                2010
                15 December 2010
                : 5
                : 119
                Affiliations
                [1 ]Division of Colon &Rectal Surgery - Department of Surgery, HUVN Granada - Spain
                [2 ]Department of Nuclear Medicine, HUVN Granada - Spain
                Article
                1748-717X-5-119
                10.1186/1748-717X-5-119
                3012041
                21159200
                d39dcb3b-4ca7-44c6-b5ca-d9f357b83d71
                Copyright ©2010 Palma et al; licensee BioMed Central Ltd.

                This is an Open Access article distributed under the terms of the Creative Commons Attribution License (<url>http://creativecommons.org/licenses/by/2.0</url>), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

                History
                : 5 September 2010
                : 15 December 2010
                Categories
                Research

                Oncology & Radiotherapy
                Oncology & Radiotherapy

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