TY - GEN
T1 - Shear wave elastography of rectal adenoma and cancer
AU - Loft, Martina Kastrup
PY - 2022/12/16
Y1 - 2022/12/16
N2 - The management of the patients with rectal adenoma or rectal cancer rely on theinitial staging. The guidelines for primary assessment of rectal cancer isrecommending a magnetic resonance imaging (MRI) scan, however, MRI has shownto overstage tumors with a low T category. Therefore, international guidelinesrecommend adding an endorectal ultrasound (ERUS). To improve the ERUSevaluation ultrasound elastography (UE) is proposed as a non-invasive technique,which provides a measurement of tissue stiffness. Two methods are available, yetshear wave elastography (SWE) is the method used in this PhD project. SWEprovides a quantitative measurement of tissue stiffness using an acoustic radiationforce impulse sent out by the transducer. A color-coded elastogram on top of Bmode image is presented on the monitor. When placing a region of interest (ROI)an elastography value is given in either meter per second (m/s) or converted intokilo Pascal (kPa). The main purpose of this PhD study was to investigate the performance of SWE in patients with rectal adenoma and rectal cancer. A literature study (paper I) was performed to evaluate the existing evidence on UE when distinguishing between benign adenoma and rectal cancer, and between adenoma and early rectal cancer (ERC). A total of six studies were including, two assessed adenoma and ERC. All studies reported an increase in diagnostic accuracy compared with ERUS and/or MRI, studies investigating ERC were limited to strain elastography. A prospective study (paper II) was conducted to assess the diagnostic accuracy of T and N classification using ERUS, SWE and diffusion-weighted MRI (DW-MRI) in patients with adenoma or ERC. Further to evaluate the association between SWE and tumor stromal fraction (SF). A total of 86 patients were included. ERUS with SWE and DW-MRI yielded high diagnostic performance. ERUS correctly classified more adenomas than DW-MRI, however the assessments were not compared to the clinical stage undertaken at the multidisciplinary team meeting but solely the histopathological stage. SWE was positively correlated with SF, which may indicate that SWE can be used as a prognostic predictor, however this needs further investigation. A reliability study (paper III) was performed to investigate the interobserver variability of SWE, T and N category assessment using ERUS, in patients with adenoma or adenocarcinoma in the rectum, between two independent operators. Further, to assess the intra- and interobserver variability between experienced andinexperienced observers, using several ROI methods, on previously obtained images. This study demonstrated a high interobserver reliability on T, and N categories, as well as SWE measurement between the two independent operators, although there were a slightly better agreement when using the men of several ROIs compared to the maximum SWE value. No differences in intra- or interobserver variability were shown between experienced and inexperienced observers, nor were there seen differences related to ROI method. In conclusion this PhD project shows that UE is a promising addition to the ERUS examination in order to distinguish between rectal adenoma and rectal cancer. ERUS with SWE correctly classified more adenomas than DW-MRI, which potentially may avoid overtreatment of patients. ERUS with SWE has a highinterrater reliability and adds valuable information when differentiating between adenoma and rectal cancer.
AB - The management of the patients with rectal adenoma or rectal cancer rely on theinitial staging. The guidelines for primary assessment of rectal cancer isrecommending a magnetic resonance imaging (MRI) scan, however, MRI has shownto overstage tumors with a low T category. Therefore, international guidelinesrecommend adding an endorectal ultrasound (ERUS). To improve the ERUSevaluation ultrasound elastography (UE) is proposed as a non-invasive technique,which provides a measurement of tissue stiffness. Two methods are available, yetshear wave elastography (SWE) is the method used in this PhD project. SWEprovides a quantitative measurement of tissue stiffness using an acoustic radiationforce impulse sent out by the transducer. A color-coded elastogram on top of Bmode image is presented on the monitor. When placing a region of interest (ROI)an elastography value is given in either meter per second (m/s) or converted intokilo Pascal (kPa). The main purpose of this PhD study was to investigate the performance of SWE in patients with rectal adenoma and rectal cancer. A literature study (paper I) was performed to evaluate the existing evidence on UE when distinguishing between benign adenoma and rectal cancer, and between adenoma and early rectal cancer (ERC). A total of six studies were including, two assessed adenoma and ERC. All studies reported an increase in diagnostic accuracy compared with ERUS and/or MRI, studies investigating ERC were limited to strain elastography. A prospective study (paper II) was conducted to assess the diagnostic accuracy of T and N classification using ERUS, SWE and diffusion-weighted MRI (DW-MRI) in patients with adenoma or ERC. Further to evaluate the association between SWE and tumor stromal fraction (SF). A total of 86 patients were included. ERUS with SWE and DW-MRI yielded high diagnostic performance. ERUS correctly classified more adenomas than DW-MRI, however the assessments were not compared to the clinical stage undertaken at the multidisciplinary team meeting but solely the histopathological stage. SWE was positively correlated with SF, which may indicate that SWE can be used as a prognostic predictor, however this needs further investigation. A reliability study (paper III) was performed to investigate the interobserver variability of SWE, T and N category assessment using ERUS, in patients with adenoma or adenocarcinoma in the rectum, between two independent operators. Further, to assess the intra- and interobserver variability between experienced andinexperienced observers, using several ROI methods, on previously obtained images. This study demonstrated a high interobserver reliability on T, and N categories, as well as SWE measurement between the two independent operators, although there were a slightly better agreement when using the men of several ROIs compared to the maximum SWE value. No differences in intra- or interobserver variability were shown between experienced and inexperienced observers, nor were there seen differences related to ROI method. In conclusion this PhD project shows that UE is a promising addition to the ERUS examination in order to distinguish between rectal adenoma and rectal cancer. ERUS with SWE correctly classified more adenomas than DW-MRI, which potentially may avoid overtreatment of patients. ERUS with SWE has a highinterrater reliability and adds valuable information when differentiating between adenoma and rectal cancer.
M3 - Ph.D. thesis
PB - Syddansk Universitet. Det Sundhedsvidenskabelige Fakultet
ER -