Objectives To evaluate interobserver agreement for T2 weighted (T2W) and diffusion-weighted MRI (DW-MRI) contours of locally advanced rectal cancer (LARC); and to evaluate manual and semi-automated delineations of restricted diffusion tumour subvolumes. Methods 20 cases of LARC were reviewed by 2 radiation oncologists and 2 radiologists. Contours of gross tumour volume (GTV) on T2W, DW-MRI and co-registered T2W/DW-MRI were independently delineated and compared using Dice Similarity Coefficient (DSC), mean distance to agreement (MDA) and other metrics of interobserver agreement. Restricted diffusion subvolumes within GTVs were manually delineated and compared to semi-automatically generated contours corresponding to intratumoral apparent diffusion coefficient (ADC) centile values. Results Observers were able to delineate subvolumes of restricted diffusion with moderate agreement (DSC 0.666, MDA 1.92 mm). Semi-automated segmentation based on the 40th centile intratumoral ADC value demonstrated moderate average agreement with consensus delineations (DSC 0.581, MDA 2.44 mm), with errors noted in image registration and luminal variation between acquisitions. A small validation set of four cases with optimised planning MRI demonstrated improvement (DSC 0.669, MDA 1.91 mm). Conclusion Contours based on co-registered T2W and DW-MRI could be used for delineation of biologically relevant tumour subvolumes. Semi-automated delineation based on patient-specific intratumoral ADC thresholds may standardise subvolume delineation if registration between acquisitions is sufficiently accurate. Advances in knowledge This is the first study to evaluate the feasibility of semi-automated diffusion-based subvolume delineation in LARC. This approach could be applied to dose escalation or ‘dose painting’ protocols to improve delineation reproducibility.
Sacral tilt represented by a steeply angled superior endplate of S1 is associated with a significantly increased angle of lordosis, between L4 and S1, and pars fractures at L5. Steep angulation of the first sacral vertebral segment maybe the predisposing biomechanical factor that leads to pincer-like impingement of the pars interarticularis and then spondylolysis.
Objective: Patients with a history of colorectal cancer are considered at increased risk of second metachronous colorectal cancer (SM-CRC), for which they frequently receive intensive colonoscopic surveillance. In view of the ambiguous nature of the existing evidence and the growing interest in targeted surveillance, we sought to quantify long-term risk with particular reference to age at diagnosis.
Method:The Surveillance Epidemiology and End Results database was used to estimate risk of SM-CRC after first incident colorectal cancer diagnosed between 1975 and 1999. We calculated time-dependent rates using Kaplan-Meier estimates and relative risk compared with the US general population.Results: From 311 689 eligible patients, there were 6387 SM-CRCs. At 15-years following initial diagnosis, the SM-CRC rate was 6.3% (95% CI, 6.1-6.5). For patients with synchronous primary cancers (n = 9936, 3.2%), the 15year SM-CRC rate increased to 10.5% (95% CI, 9.1-12.2). Younger age predicted for increased relative risks but absolute cumulative rates at 15 years were low (Table).Conclusion: The long-term cumulative risk of SM-CRCs after first colorectal cancer is low, even among younger age patients. These data do not support the routine use of high-frequency colonoscopy surveillance in patients with a history of colorectal cancer.
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