USEFULNESS OF STRUCTURED MRI REPORT TEMPLATES PROPOSED BY THE EUROPEAN SOCIETY OF GASTROINTESTINAL AND ABDOMINAL RADIOLOGY IN T AND N STAGING OF RECTAL CANCER

The definition of T and N stage is crucial for a correct therapeutic management of patients with colorectal cancer. Nowadays, MR imaging (MRI) is considered the best available tool for rectal cancer staging, allowing an accurate evaluation of the disease extent, up to, beyond and over the mesorectal fascia, and of the lymph nodes involvement. MRI and it is also routinely performed after neoadjuvant chemo-radiation therapy (nCRT) for the to evaluateion of the response to treatments and for surgical planning. In 2012, the European Society of Gastrointestinal and Abdominal Radiology (ESGAR) initiated an expert consensus meeting on magnetic resonance imaging (MRI) for the clinical management of rectal cancer management. In 2016, the ESGAR updated the previous recommendations and proposed a novel report template, (both for primary staging and for restaging after nCRT) based on the additional information obtained by the diffusion weighted images sequence in the MR protocol. Moreover, in the 2016 recommendation paying more attention was paid to the morphological and signal characteristic of the lymph nodes, in order to better identify the N stage. The aim of this study was to evaluate the usefulness and to compare the 2012 and 2016 structured MRI report templates proposed by the European Society of Gastrointestinal and Abdominal Radiology (ESGAR), for the rectal cancer staging of the rectal cancer. Material and Methods: This study included Forty-seven 47 consecutive patients (M:F, 34:13; mean age 63.9±12.4 years, range 30-86 years) with affected by biopsy-proven rectal cancer, were included in this retrospective study. Nineteen out of 47 19 of which had undergone nCRT (Capecitabine and Oxaliplatin, plus a total of 50.4Gy radiation dose) before surgery due to the locally advanced stage. All patients performed aunderwent MRI examination within 20 days before surgery. In 44/47 cases the an anterior rectal anterior resection (RAR) was performed; in the remaining while in 3 cases anthe abdominoperineal resection (APR) was preferred. Twelve resections were performed by using the open-approach (10 RARs and 2 APRs), 10 by laparoscopy (all RARs) and 25 by the robotic-approach (24 RARs and one APR). A comparison between the pathological and the radiological TN staging obtained according to the 2012 as well as the 2016 ESGAR guidelines, and the pathological TN staging was performed. Results: The radiological T stage did not differ between 2012 and 2016 ESGAR guidelines. In the directly resected group the radiological T stageit was T1, T2, T3 and T4 in 1, 5, 20 and 2 patients, respectively. As to the patients who underwent nCRT, it was T0 (complete response without lesion detection or residual fibrotic tissue), T2, T3 and T4 in 4, 7, 6 and 2 patients, respectively. A statistical correlation was found between the radiological and pathological T stage (p<0.0001; ρ of Spearman=0.62). As to the radiological N stage, according to 2012 and 2016 guidelines: no metastatic lymph nodes were found in 24 and 32 patients, respectively; N1 stage was assessed in 22 and 14 patients respectively,. The N2 stage was assessed only in one patient, according to both guidelines. The pathological N stage was N0, N1 and N2 in 27, 16 and 4 patients, respectively. A statistical correlation was found between the radiological-pathological N stage comparison by applying both the 2012 (p=0.009) and the 2016 guidelines (p<0.0001); however, the updated 2016 version showed a stronger correlation (ρ of Spearman=0.60). Conclusion: Both the 2012 and the 2016 ESGAR structured MRI report templates were are reliable tools to assess the radiological T and N stage of the rectal cancer; the 2016 report template wais more accurate in estimating lymph-nodes involvement.