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

<p>Abstract</p> <p>Background</p> <p>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).</p> <p>Methods</p> <p>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.</p> <p>Results</p> <p>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_maxvalues 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.</p> <p>Conclusions</p> <p>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.</p>

Abstract licence: CC BY-NC-ND

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