Background: To evaluate the influence of patient positioning on target dose coverage and dose distribution to the small bowel in intensity-modulated radiation therapy (IMRT) for rectal cancer patients.Methods: Twenty-four consecutive rectal cancer patients undergoing postoperative radiation were selected and set up in either a prone or supine position. All patients received computed tomography (CT) scans before and during treatment (1-4 weeks). The CT images were defined as plan, 1W, 2W, 3W, or 4W. The plan, 1W, 2W, 3W and 4W CT images were fused. The clinical target volume (CTV) and planning target volume (PTV) delineated on the plan CT were copied onto the 1-4W CT. The treatment plans based on the plan CT were also copied onto the 1-4W CT. The target dose coverage rate was assessed. The couchposition data of the linear accelerator were acquired.Results: Failure rates of the CTV and PTV target dose coverage were higher in the prone group than in the supine group (18.60% vs. 0% and 69.76% vs. 53.65%) during the treatment. The total couch-position deviation for the prone group (1.23±0.76 cm) was significantly greater than that of the supine group (0.28± 0.18 cm; P=0.001). Compared with the supine group, the prone group had significantly less irradiated small bowel volume at V5 (P=0.003) and V10 (P=0.004). Conclusions:The supine position maintained better target dose coverage and setup reproducibility in rectal cancer patients treated with IMRT. The prone position combined with the belly board can reduce the dose received by the small bowel.
e12091 Background: With the rapid development of MRI scanning technology , DCE-MRI in breast cancer has been one of the most sensitive examinations for the reason of allowing precise imaging, which can be helpful to demonstrate and evaluate the anatomical structures of breast cancer and its surrounding. What is more,through application of postprocessing technique of MRI,quantitative and half-qualitative data can be obtained for the diagnosis and the differential diagnosis of breast cancer. It is reported that the recurrence of breast cancer after breast conserving surgery is related with elevated BEC of MRI before operation as the result of the difficulty to find the micro-lesions and the margin of infiltrative lesions. Objective: Study on the relationship between the background enhancement coefficient of breast cancer under MRI before operation and recurrence of postoperative chest wall. Material and Methods: 194 cases of breast cancer patients undergoing radical surgery were retrospectively analyzed, all of which were confirmed by pathology and molecular classification.Before surgery all the patients did MRI and the BEC was measured.Aim for study on the relevance of the elevated BEC and chest wall recurrence,we investigate the relationship between the stage, grade,molecular subtype of breast cancer and the elevated BEC statistically. Results: The elevated BEC of the breast before operation is associated with chest wall recurrence after operation (P=0.045), and high expression of HER-2 (P=0.07). Multiple lesions of breast cancer and Ki-67>14% also appeared to be associated with the elevated BEC (P=0.08).While there seem to be no correlation between the size of tumor ,LN metastases, nuclear and pathological grade,molecular typing, PR expression,ER expression, status of the LN capsule and the elevated BEC. Conclusions: The elevated BEC of breast before operation is an independent prognostic factor for chest wall recurrence after operation.Given BEC get a potential to make a brand new biomarker for breast cancer,further relevant research is needed.
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