SFMR:s studentpris 2021

SFMR:s studentpris för bästa vetenskapliga studentarbete med anknytning till radiologi eller nukleärmedicin inom läkarprogrammet 2021 tilldelas Elice Ståhl

Titel: Staging of rectal cancer: the correlation between histopathology and PET/MR

Supervisors: Katrine Riklund Miriam Rutegård Jan Axelsson Department: Strålningsvetenskaper, Diagnostisk Radiologi, Umeå Universitet

Background: Every year approximately 2000 new cases of rectal cancer are diagnosed in Sweden. The different therapies used to treat rectal cancer is chemotherapy, radiotherapy, and surgery which can be combined in different ways. The choice of treatment is based on the stage of cancer at diagnosis. Local spread of the tumour is evaluated with an MRI examination.

Aim: The purpose of this study was to determine if the diagnostic accuracy of staging rectal cancer with a combined PET/MRI is higher than the methods used today.

Methods: twenty-two patients with rectal cancer were included and examined with a combined PET/MRI. All mesorectal nodal structures, i.e. all round or oval shaped structures assessed as lymph nodes, found on the MRI images were evaluated as either benign or suspected malignant and if feasible, inidividually anatomically matched to the histopathological assessment. PET measurements were made on all matched structures. SUVmax values of all structures were obtained.

Results: MRI as a single examination showed an overall sensitivity and specificity of 34% and 95%, respectively, and for lymph nodes >5mm 95% and 25% respectively. The combined PET/MRI showed a sensitivity and specificity of 36% and 98%, respectively when using a SUVmax threshold of 2.0. It was mainly the malignant structures less than 5mm and the benign lesions larger or equal to 5mm that were assessed incorrectly.

Conclusion: This study shows that a combined PET/MRI is comparable with MRI alone when staging rectal cancer. There are mainly the malignant structures that are <5mm that are incorrectly assessed with all modalities.