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

Silvia Girolama Drago, Abstract Co-Author: Nothing to Disclose

Giulia Querques MD, Abstract Co-Author: Nothing to Disclose

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

To assess the clinical diagnostic value of functional imaging, combining quantitative parameters of ADC and SUV max, before and after chemo-radiation therapy, in prediction of tumor response of patients with rectal cancer, related to tumor regression grade at histology.

A total of 51 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 including DW imaging for staging (PET 1, RM1) and after completion (6.6.weeks) of neoadjuvant chemoradiation treatment (PET 2, RM 2). Subsequently all patients underwent total mesorectal excision and the histological results were compared with imaging findings. The MR scanning, performed on 1,5 T magnet (Philips,Achieva), included T2-weighted multiplanar imaging and in addition DW images with b-value of 0 and 1000 mm²/sec. On PET/CT the SUV max 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,TRG 5= no regression).

At histology,according to Mandard’s criteria,33 tumors(68%) showed complete or subtotal regression(TRG1-2) and were classified as responders;18 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 PET2 (p<0.001),whereas mean ADC values was lower in MR 1 than MR2 (p<0.001).The best predictors for TRG response were SUV2(threshold of 4.4) and ADC2(1.28x10-3mm2/s); combining in a single analysis median quantitative value, the PPV in predicting different group category response,related to TRG system,presented an overall AUC of 96%, higher than DWI(88.2%) or SUVmax(93.3%).

In era of PET/MRI the combination of functional data derived from DWI and PET/CT represents the most accurate method to evaluate the response to treatment in LARC patients, with repeatable accuracy values higher than those reported for other conventional imaging techniques.

The functional imaging combining ADC and SUVmax permits to detect changes in cellular tissue structures useful for the assessment of tumour response after the neoadjuvant therapy in rectal cancer patients.

Ippolito, D, Bonaffini, P, Fior, D, Drago, S, Querques, G, Sironi, S, Combined Predictive Value of Functional Imaging Markers Derived from Correlations of PET/CT and Diffusion Weighted MRI in Response Assessment of Rectal Cancer Treatment after Neoadjuvant Radiochemotherapy.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14008450.html