On preoperative treatment selection and magnetic resonance imaging in rectal cancer

Abstract

In Sweden, 2000 patients are diagnosed with rectal cancer annually. Developments in surgery have improved survival and the addition of preoperative radiotherapy (RT) or chemoradiotherapy (CRT) has reduced local recurrence rates to 5 %. However, (C)RT is associated with side effects. In order to achieve balance between improved outcomes and risk of treatment-associated morbidity, optimized treatment selection is crucial. Guidelines for rectal cancer management are mainly based on tumour characteristics from magnetic resonance imaging (MRI). Thus, correct interpretation of MRI is essential for optimal selection. In addition, all pre-therapeutic information available, e.g. on age and comorbidity, should ideally be taken into consideration in treatment-decisions. The aim of this thesis was to increase the knowledge regarding preoperative treatment selection in rectal cancer.

Paper I aimed at evaluating the influence of pretherapeutic parameters on preoperative treatment selection. Patients undergoing elective abdominal rectal cancer surgery 2000-2010 in the Stockholm-Gotland region were included (n = 2619). Patients with comorbidity or old age (≥ 80 years) received less preoperative (C)RT. Deviations from guideline recommendations regarding preoperative (C)RT were revealed.

From the study cohort of paper I, patients with stage I-III tumours were included in Paper II (n = 2300). The influence of age and comorbidity on long-term outcome after preoperative (C)RT, was evaluated. Overall, preoperative (C)RT did not influence long-term outcome but in patients with comorbidity overall survival was improved following preoperative (C)RT whereas no significant differences were seen among the elderly (≥ 80 years).

The objective of Paper III was to investigate the performance and reporting of rectal cancer MRI and the influence on preoperative treatment selection. MRI investigations and reports on 94 patients were re-evaluated. Predefined standards for rectal cancer MRI were not universally applied. Because of incomplete original reports, clinical tumour staging was possible in only 70 % of the patients. The agreement was unsatisfactory both regarding tumour staging between the re-evaluation and the original reports and regarding treatment selected compared to recommended after re-evaluation.

Paper IV assessed the MRI characteristics of the primary tumour regarding prediction of outcomes after surgery for local recurrence. Treatment selection for the primary tumour was also evaluated. Patients undergoing surgery for local recurrence 2003-2013 at Karolinska University Hospital were included (n = 54). No factors on primary tumour MRI were found to predict long-term outcomes after surgery for local recurrence. However, a MRI-detected primary tumour response to preoperative (C)RT correlated to fewer R0 resections of the local recurrence. Only 11 of 30 patients with locally advanced primary tumour received preoperative CRT.