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?

Abstract

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.

Value of diffusion-weighted imaging in the detection of viable tumour after neoadjuvant chemoradiation therapy in patients with locally advanced rectal cancer: comparison withT2weighted and PET/CT imaging

“…Although standardised histological examination procedures were used and detailed pathology reports were provided by an experienced pathologist, exact matching between the MR images and histopathological findings for the viable tumour may have been suboptimal. Second, the percentage of complete histopathological responders in our study was 12%, a rate similar to that found by others [20,23,24,[42][43][44]. The small number of cases with pathological CR might, however, have led to overestimation of diagnostic accuracy.…”

“…Many investigators have reported a substantial decrease in standardised uptake value (SUV) post-CRT in responders compared with nonresponders [19][20][21][22]. However, only a few studies have compared the abilities of MRI and PET/CT to enable prediction of responses to neoadjuvant CRT [23,24]. There has been no published comparative study of DWI and PET/CT in the evaluation of tumour viability after neoadjuvant CRT in locally advanced rectal cancer.…”

Monitoring and Predicting Response to Therapy with 18F-FDG PET in Colorectal Cancer: A Systematic Review

“…As shown in Table 3, 15 studies of multimodality treatment (chemoradiation with or without regional hyperthermia) response monitoring were performed (44,47,(49)(50)(51)(52)(53)(54)(55)(56)(57)(58)(59)(60)(61). Several of these studies (44,50-52,58) compared metabolic and morphologic response evaluations.…”

PET/MRI: Reliability/Reproducibility of SUV Measurements

“…PERCIST 1.0 suggested a cutoff at 30% increase for progressive disease and 30% decrease for partial remission, which is a slight increase in difference compared to the 25% according to the 1999 EORTC recommendation. A study comparing both evaluation systems for response assessment in metastatic colorectal cancer came to the conclusion that they were equivalent [35]; however, several studies comparing CT-based RECIST with FDG quantification found that PET was superior in predicting histopathological therapy response [36,37], time to progression [38], or overall survival [39]. Besides the increasing use of FDG PET for therapy response assessment, baseline quantitative PET metrics are also increasingly used to predict outcome.…”