MR imaging and spectroscopy in prostate and colon cancer diagnostics
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Prostate and colorectal cancers are among the most common cancers in Norway and are also leading causes of cancer related deaths. In prostate cancer there are currently no accurate clinical methods to discriminate patients in immediate need of treatment from patients with clinically insignificant cancers that can postpone curative treatment. This leads to substantial overtreatment and potentially side-effects for this group of patients. In colon cancer, highthroughput methods to classify tumours according to known prognostic markers (e.g. MSI status) and a better understanding of tumour biology is important for optimized personalized treatment. There is therefore a need for additional diagnostic and prognostic tools to increase survival and secure good quality of life. The main objective of this thesis was to test the feasibility and accuracy of different MR methods in the diagnostics of prostate and colon cancer. With a multiparametric MR examination of the prostate, combining T2-weighted imaging, diffusion weighted imaging, dynamic contrast-enhanced MRI, and/or MR spectroscopic imaging the entire gland can be examined non-invasively for metabolic, cellular, morphological and vascular changes associated with the disease. In this thesis, a multiparametric MR examination was performed on a 3 T system without an endorectal coil and a significant difference in mean values between cancer and non-cancer areas were observed for all MR parameters analyzed. Further, any combination of MR parameters was better than T2WI alone in separating cancer and non-cancer areas. These findings show that a multiparametric MR examination without an endorectal coil is feasible and accurate and can contribute to improve the diagnostic pathway of prostate cancer patients, avoiding patient discomfort and high cost. High resolution magic angle spinning (HR MAS) MR spectroscopy is an ex vivo method providing detailed metabolic information (metabolite profiles) of intact tissue samples. With sophisticated multivariate analysis, these metabolite profiles can be used to discriminate between cancer and non-cancer tissue and to discriminate between tissue samples of different classes such as aggressiveness (Gleason score) in prostate cancer and MSI status in colon cancer. In this thesis, discrimination between cancer and non-cancer tissue samples based on the metabolic profile has been demonstrated both for colon and prostate cancer. Further, classification of MSI status of samples from colon cancer patients and of aggressiveness of samples from prostate cancer patients was shown to have high accuracy. Magnetic resonance spectroscopy can be performed both on tissue samples ex vivo and on patients in vivo during a clinical MR examination and as a part of this thesis the hypothesis that metabolic ratios measured in vivo correlate with profiles measured ex vivo from the same locations was tested. Indeed, a strong correlation between in vivo and ex vivo prostate spectroscopy measurements was observed. This indicates that HR MAS can adequately represent the in vivo metabolic profile of the cancer and that diagnostic and prognostic biomarker findings from ex vivo studies of tissue samples can be translated to in vivo patient examinations. In conclusion, the work presented in this thesis show that MRI and MRS are useful methods in diagnostics of colon and prostate cancer with the ability to discriminate between cancer and non-cancer, and that the methods also have a potential in prognostics by MSI and Gleason score classification.
UtgiverNorges teknisk-naturvitenskapelige universitet, Det medisinske fakultet, Institutt for sirkulasjon og bildediagnostikk
SerieDoktoravhandlinger ved NTNU, 1503-8181; 2012:251
Dissertations at the Faculty of Medicine, 0805-7680; 566