MRI Imaging or CT Abdomen as Standard Work-up Before Treatment Planning for Rectal Cancer?

Overview

Rectal cancer is a common diagnosis. The prognosis after treatment has improved over the last decades, partly due to neoadjuvant radio(chemo)therapy, but also due to improved surgical technique (TME) and, in certain cases, due to adjuvant therapy after surgery. For some 15-20 years, treatment of metastasis has changed; liver- and lung metastasis in certain situations are surgically removed, or in the liver, treated with ablation (radio-frequency). During the same period the possibilities for chemotherapy of metastatic disease have improved, with new drugs and more drug regimens. These changes in treatment pathways have required changes in how patients with newly diagnosed rectal cancer are "worked up" pre-treatment. Starting in the early 2000s magnetic resonance imaging of the pelvic area has developed and is today mandatory to be able to adequately stage the tumour and plan for the multi-modal treatment before and after surgery. In many hospitals the set-up is a combination of computed tomography of the abdomen and chest and to this a MRI of the pelvic organs is added, whereas others have adopted MRI also for the abdominal part, thus having an MRI of the liver for the diagnosis of liver metastasis initially, before surgery. For the chest organs, CT is still normative. MRI has a higher sensitivity and specificity to detect liver metastasis, compared with CT. In order to plan the liver surgery/ablations, most liver surgeons rely on MRI for detailed information about the position of the metastasis and the relation to large vessels. The aim of this study is to examine the possible differences in percentage of patients requiring further radiology examinations after basic set-up comparing the routine of initial MRI of abdomen (and pelvic organs) with the routine of initial CT of the abdomen (and MRI of the pelvic organs). Further included is an analysis of the rate of liver metastasis using the two different routines, and finally outcome over 12 months in terms of liver treatment for metastasis.

Background: Rectal cancer is a common diagnosis in both men and women, more commonly occurring in men (60%) than women (40%). In Sweden some 2000 cases are diagnosed each year. The prognosis after treatment has improved over the last decades, partly due to neoadjuvant radio(chemo)therapy, but also due to improved surgical technique (TME) and, in certain cases, due to adjuvant therapy after surgery. For some 15-20 years, treatment of metastasis has changed; liver- and lung metastasis in certain situations are surgically removed, or in the liver, treated with ablation (radio frequency). During the same period the possibilities for chemotherapy of metastatic disease have improved, with new drugs and more drug regimens. These changes in treatment pathways have required changes in how patients with newly diagnosed rectal cancer are "worked up" pre-treatment. Starting in the early 2000s magnetic resonance imaging of the pelvic area has developed and is today mandatory to be able to adequately stage the tumour and plan for the multi-modal treatment before and after surgery. In many hospitals the set-up is a combination of computed tomography of the abdomen and chest and to this a MRI of the pelvic organs is added, whereas others have adopted MRI also for the abdominal part, thus having an MRI of the liver for the diagnosis of liver metastasis initially, before surgery. For the chest organs, CT is still normative. MRI has a higher sensitivity and specificity to detect liver metastasis, compared with CT. In order to plan the liver surgery/ablations, most liver surgeons rely on MRI for detailed information about the position of the metastasis and the relation to large vessels. The objective of the study is to examine: The possible differences in percentage of patients requiring further radiology examinations after basic set-up comparing the routine of initial MRI of abdomen (and pelvic organs) with the routine of initial CT of the abdomen (and MRI of the pelvic organs). Further included is an analysis of the rate of liver metastasis using the two different routines, and finally outcome over 12 months in terms of liver treatment for metastasis. Hypothesis: Primary: • Patients who underwent initial abdominal MRI had a significantly lower need for additional radiology examinations compared with those who underwent initial CT abdomen. Secondary: * A higher proportion of patients who underwent initial abdominal MRI underwent liver treatment aiming for cure at 12 months. * Abdominal MRI as initial examination resulted in a higher proportion of detected liver metastasis. * Cost effectiveness analysis will show that initial abdominal MRI of the abdominal organs is cost-effective. Design: A retrospective study using clinical details such as date for diagnosis, clinical tumour stage, type of surgical treatment and date, pathology tumour stage, local recurrence and survival at 36 months from the Swedish ColoRectal Cancer Registry for patients with rectal cancer treated at Sahlgrenska University Hospital and Norra Älvsborg Hospital during the years collecting patients backwards from 2015-12-31 until sufficient number is reached (see below "Sample size"). Data will be collected in the radiology patient documentation at the two hospitals using the original radiology report for the index examinations as well as type and number of additional radiology examinations and the reports for those. For patients with liver metastases in the original radiology report at the index work-up and in cases with indeterminate initial results, the original radiology examinations will be re-evaluated by one or if possible two radiologists. Data from the clinical patient records on treatment plan (index treatment) and time and type of treatment for liver metastasis. No direct contact with patients is planned, and only data already collected (see above) will be used. Methodology: Through Regional Cancer Center West (RCC Väst) appropriate data from to Swedish ColoRectal Cancer Register will be collected, consisting of age, time for diagnosis, time for multidisciplinary conference, time for oncological treatment, time for surgery, cTNM as well as pTNM, performed treatment/s within 12 months, recurrence/s and survival (3 years). Data to be collected from radiology reports include presence of liver metastasis, number of liver metastasis, additional radiology examinations after index work-up - type and number as well as findings of liver metastasis. Additional findings of distant metastases to retro peritoneal lymph-nodes and to peritoneum will also be recorded. Data from re-evaluation of examinations for all patients diagnosed with liver metastases such as number of metastases, number of small metastases (\<10mm), metastases to retro peritoneal lymph-nodes and to peritoneum. Data to be collected from hospital records for all patients include time line for different aspects of treatment including multidisciplinary conference (and decision), oncological treatment and liver surgery until 12 months from diagnosis.