Davide Ippolito MD, Presenter: Nothing to Disclose

Pietro Andrea Bonaffini MD, Abstract Co-Author: Nothing to Disclose

Davide Fior MD, Abstract Co-Author: Nothing to Disclose

Cristina Capraro MD, Abstract Co-Author: Nothing to Disclose

Chiara Trattenero MD, Abstract Co-Author: Nothing to Disclose

Sandro Sironi MD, Abstract Co-Author: Nothing to Disclose

To determine the clinical value of functional imaging by analyzing quantitative parameters of ADC and SUV max values before and after chemo-radiation therapy in prediction of tumor response of patients with rectal cancer, correlated with the histologic examination expressed as tumor regression grade.

A total of 45 patients with biopsy proven diagnosis of rectal carcinoma were enrolled in our study.All patients underwent a whole body 18 FDG PET/CT scan and a pelvic MR examination before(PET 1,MR 1) and after the neoadjuvant chemoradiation therapy(PET 2,MR 2).Subsequently all patients underwent total mesorectal excision and the histological results were compared with imaging findings.MR scanning,performed on 1,5 T magnet(Philips,Achieva),comprised T2-weighted multiplanar imaging and in addition DW images with b-value of 0 and 1000 mm²/sec. On PET/CT the SUVmax of the rectal lesion were calculated in PET1 and PET2. The percentage decrease of SUVmax(ΔSUV) and ADC(ΔADC) values from baseline to presurgical scan were assessed and correlated with pathologic response classified as tumor regression grade (Mandard’s criteria;TRG 1= complete regression,TRG5= no regression).

At histological examination,according to Mandard’s criteria, 29 tumors(68%) showed complete or subtotal regression(TRG1-2) and were classified as responders;16 tumors(32%) were classified as non-responders(TRG3-5).Considering all patients the mean values of SUVmax in PET 1 was higher than mean value of SUVmax in PET 2 (p<0.001),whereas mean ADC values was lower in MR 1 than MR 2 (p<0.001),with a ΔSUV and ΔADC respectively of 67% and 69%.The best predictors for TRG response were SUV2 (threshold of 4.4) and ADC2 (1.28x10-3mm2/s) with high sensitivity and specificity.Combining in a single analysis median quantitative value, the PPV in predicting the different group category response, related to TRG system,presented an AUC of 96%, higher than DWI (88.2%) or SUVmax (93.3%).

Combination of PET-CT and MR imaging, evaluating changes in glucose metabolism and ADC, allows the identification of spatially distinct regional responses to therapy within tumor tissues, with higher sensitivity than either method alone.

In era of PET/MRI scanner, the combination of DWI and PET/CT represents the most feasible method to evaluate LARC patients,with accuracy values higher than those reported for other imaging technique.

Ippolito, D, Bonaffini, P, Fior, D, Capraro, C, Trattenero, C, Sironi, S, Neoadjuvant Radiochemotherapy Response Evaluation with Magnetic Resonance and FDG-PET/CT in Rectal Cancer Patients: Predictive Value of Combined Quantitative Parameters of ADC and SUV Compared with TRG at Histology.  Radiological Society of North America 2013 Scientific Assembly and Annual Meeting, December 1 - December 6, 2013 ,Chicago IL. http://archive.rsna.org/2013/13018605.html