***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: PURPOSE To quantify the inter-fraction shape variation of the mesorectum for rectal cancer patients treated with 5 x 5 Gy in supine position  and compare it to variation in prone position . METHODS AND MATERIAL S For 28 patients a planning CT ( pCT ) and five daily cone-beam-CT ( CBCT ) scans  were acquired in supine position . The mesorectal part of the CTV ( MesoRect ) was delineated on all scans . The shape variation was quantified by the distance between the pCT- and the CBCT delineations and stored in surface maps after online setup correction . Data were analyzed for male and female patients separately and compared to prone data . RESULTS A large range of systematic , 1 - 8 mm ( 1SD ) , and r and om , 1 - 5 mm , shape variation was found , comparable to prone patients . R and om-shape variation was comparable for male and female patients , while systematic variation was 3 mm larger for female patients . CONCLUSIONS Shape variation of the MesoRect is substantial , heterogeneous and different between male and female patients . Differences between supine and prone orientation , however , are small . Clinical margins should be differentiated in position along the cranio-caudal axis , in anterior-posterior direction and for gender . Margins should also be increased , even when online setup correction is used . Due to the small margin differences between prone and supine treatments , the setup choice should be determined on dose to the organs at risk PURPOSE To develop a Radiation Therapy Oncology Group ( RTOG ) atlas of the elective clinical target volume ( CTV ) definitions to be used for planning pelvic intensity-modulated radiotherapy ( IMRT ) for anal and rectal cancers . METHODS AND MATERIAL S The Gastrointestinal Committee of the RTOG established a task group ( the nine physician co- authors ) to develop this atlas . They responded to a question naire concerning three elective CTVs ( CTVA : internal iliac , presacral , and perirectal nodal regions for both anal and rectal case planning ; CTVB : external iliac nodal region for anal case planning and for selected rectal cases ; CTVC : inguinal nodal region for anal case planning and for select rectal cases ) , and to outline these areas on individual computed tomographic images . The imaging files were shared via the Advanced Technology Consortium . A program developed by one of the co- authors ( I.E.N. ) used binomial maximum-likelihood estimates to generate a 95 % group consensus contour . The computer-estimated consensus contours were then review ed by the group and modified to provide a final contouring consensus atlas . RESULTS The panel achieved consensus CTV definitions to be used as guidelines for the adjuvant therapy of rectal cancer and definitive therapy for anal cancer . The most important difference from similar atlases for gynecologic or genitourinary cancer is mesorectal coverage . Detailed target volume contouring guidelines and images are discussed . CONCLUSION This report serves as a template for the definition of the elective CTVs to be used in IMRT planning for anal and rectal cancers , as part of prospect i ve RTOG trials Summary Background Preoperative or postoperative radiotherapy reduces the risk of local recurrence in patients with operable rectal cancer . However , improvements in surgery and histopathological assessment mean that the role of radiotherapy needs to be reassessed . We compared short-course preoperative radiotherapy versus initial surgery with selective postoperative chemoradiotherapy . Methods We undertook a r and omised trial in 80 centres in four countries . 1350 patients with operable adenocarcinoma of the rectum were r and omly assigned , by a minimisation procedure , to short-course preoperative radiotherapy ( 25 Gy in five fractions ; n=674 ) or to initial surgery with selective postoperative chemoradiotherapy ( 45 Gy in 25 fractions with concurrent 5-fluorouracil ) restricted to patients with involvement of the circumferential resection margin ( n=676 ) . The primary outcome measure was local recurrence . Analysis was by intention to treat . This study is registered , number IS RCT N 28785842 . Findings At the time of analysis , which included all participants , 330 patients had died ( 157 preoperative radiotherapy group vs 173 selective postoperative chemoradiotherapy ) , and median follow-up of surviving patients was 4 years . 99 patients had developed local recurrence ( 27 preoperative radiotherapy vs 72 selective postoperative chemoradiotherapy ) . We noted a reduction of 61 % in the relative risk of local recurrence for patients receiving preoperative radiotherapy ( hazard ratio [ HR ] 0·39 , 95 % CI 0·27–0·58 , p<0·0001 ) , and an absolute difference at 3 years of 6·2 % ( 95 % CI 5·3–7·1 ) ( 4·4 % preoperative radiotherapy vs 10·6 % selective postoperative chemoradiotherapy ) . We recorded a relative improvement in disease-free survival of 24 % for patients receiving preoperative radiotherapy ( HR 0·76 , 95 % CI 0·62–0·94 , p=0·013 ) , and an absolute difference at 3 years of 6·0 % ( 95 % CI 5·3–6·8 ) ( 77·5 % vs 71·5 % ) . Overall survival did not differ between the groups ( HR 0·91 , 95 % CI 0·73–1·13 , p=0·40 ) . Interpretation Taken with results from other r and omised trials , our findings provide convincing and consistent evidence that short-course preoperative radiotherapy is an effective treatment for patients with operable rectal cancer . Funding Medical Research Council ( UK ) and the National Cancer Institute of Canada BACKGROUND Postoperative chemoradiotherapy is the recommended st and ard therapy for patients with locally advanced rectal cancer . In recent years , encouraging results with preoperative radiotherapy have been reported . We compared preoperative chemoradiotherapy with postoperative chemoradiotherapy for locally advanced rectal cancer . METHODS We r and omly assigned patients with clinical stage T3 or T4 or node-positive disease to receive either  preoperative or postoperative chemoradiotherapy . The preoperative treatment consisted of 5040 cGy delivered in fractions of 180 cGy per day , five days per week , and fluorouracil , given in a 120-hour continuous intravenous infusion at a dose of 1000 mg per square meter of body-surface area per day during the first and fifth weeks of radiotherapy . Surgery was performed six weeks after the completion of chemoradiotherapy . One month after surgery , four five-day cycles of fluorouracil ( 500 mg per square meter per day ) were given . Chemoradiotherapy was identical in the postoperative-treatment group , except for the delivery of a boost of 540 cGy . The primary end point was overall survival . RESULTS Four hundred twenty-one patients were r and omly assigned to receive preoperative chemoradiotherapy  and 402 patients to receive postoperative chemoradiotherapy . The overall five-year survival rates were 76 percent and 74 percent , respectively ( P=0.80 ) . The five-year cumulative incidence of local relapse was 6 percent for patients assigned to preoperative chemoradiotherapy and 13 percent in the postoperative-treatment group ( P=0.006 ) . Grade 3 or 4 acute toxic effects occurred in 27 percent of the patients in the preoperative-treatment group , as compared with 40 percent of the patients in the postoperative-treatment group ( P=0.001 ) ; the corresponding rates of long-term toxic effects were 14 percent and 24 percent , respectively ( P=0.01 ) . CONCLUSIONS Preoperative chemoradiotherapy , as compared with postoperative chemoradiotherapy , improved local control and was associated with reduced toxicity but did not improve overall survival PURPOSE To determine the reduction of prostate motion during a typical radiotherapy  ( RT ) fraction from a bowel regimen comprising an antiflatulent diet and daily milk of magnesia . METHODS AND MATERIAL S Forty-two patients with T1c-T2c prostate cancer voided the bladder and rectum before three cinematic magnetic resonance imaging scans obtained every 9 s for 9 min in a vacuum immobilization device . The MRIs were at baseline without bowel regimen ( MRI-BL ) , before CT planning with bowel regimen ( MRI-CT ) , and before a r and omly assigned RT fraction ( 1 - 42 ) with bowel regimen ( MRI-RT ) . A single observer tracked displacement of the posterior midpoint ( PM ) of the prostate . The primary endpoints were comparisons of the proportion of time that the PM was displaced > 3 mm ( PTPM3 ) from its initial position , and the secondary endpoints were comparisons of the reduction of initial rectal area , with and without the bowel regimen . RESULTS The mean rectal area was : 13.5 cm(2 ) at MRI-BL , 12.7 cm(2 ) at MRI-CT , and 12.3 cm(2 ) at MRI-RT ( MRI-BL vs. MRI-CT , p = 0.11 ; MRI-BL vs. MRI-CT , p = 0.07 ) . Moving rectal gas alone ( 56 % ) and moving gas and stool ( 18 % ) caused 74 % of intrafraction prostate motion . The PTPM3 was 11.3 % at MRI-BL , 4.8 % at MRI-CT , and 12.0 % at MRI-RT ( MRI-BL vs. MRI-CT , p = 0.12 ; MRI-BL vs. MRI-RT , p = 0.89 ) . CONCLUSION For subjects voiding their rectum before imaging , an antiflatulent diet and milk of magnesia laxative did not significantly reduce initial rectal area or intrafraction prostate motion Background and Purpose : In locally advanced rectal cancer , neoadjuvant radiochemotherapy is indicated . To improve target volume definition for radiotherapy planning , the potential of implanted gold markers in the tumor region was evaluated . Patients and Methods : In nine consecutive patients , two to three gold markers were implanted in the tumor region during rigid rectoscopy . Computed tomography scans were performed during treatment planning . All electronic portal imaging devices ( EPIDs ) recorded during treatment series were analyzed . All patients underwent complete tumor resection with meticulous histopathologic examination . Results : The gold markers could easily be implanted into the mesorectal tissue at the caudal tumor border without any complications . They were helpful in identifying the inferior border of the planning target volume in order to spare normal tissue ( in particular anal structures ) . No significant shift of the markers was found during the course of therapy . Marker matching of the EPIDs did not improve patient positioning in comparison to bone structure matching . The former position of at least one marker could be identified in all patients during histopathologic examination . Conclusion : The use of gold marker enables a more precise definition of the target volume for radiotherapy in patients with rectal cancer . This could eventually allow a better protection of anal structures of patients with a tumor localization ≥ 5 cm cranial of the anal sphincter . The implantation of the gold markers improved communication between the surgeon , the radiooncologist and the pathologist result ing in intensified exchange of relevant informations . Hintergrund und Ziel : Bei Patienten mit fortgeschrittenem Rektumkarzinom ist eine neoadjuvante Radiochemotherapie indiziert . Um die Definition des Zielvolumens zu verbessern , wurde das Potential von implantierten Goldmarkern in der Tumorregion untersucht . Patienten und Method ik : Bei neun konsekutiven Patienten wurden während der prätherapeutischen starren Rektoskopie zwei bis drei Goldmarker in die Tumorregion implantiert . Für die Bestrahlungsplanung wurden computertomographische Bilder aufgenommen . Alle während der Bestrahlung aufgenommenen Portal-Image-Bilder wurden analysiert . Alle Patienten erhielten eine komplette Tumorresektion mit anschließender histopathologischer Untersuchung . Ergebnisse : Die Goldmarker konnten einfach und komplikationslos in das mesorektale Gewebe am kaudalen Tumorr and gelegt werden . Sie waren hilfreich bei der Identifikation des unteren Tumorr and s während der Bestrahlungsplanung , um Normalgewebe ( insbesondere die analen Strukturen ) bei der Bestrahlung schonen zu können . Es f and sich keine signifikante Verschiebung der absoluten Markerpositionen während der Bestrahlung . Eine Korrektur der Lagerung der Patienten nach Markern ergab keinen Vorteil gegenüber der Korrektur mit knöchernen L and marken . Die ehemalige Position von mindestens einem Marker konnte bei jedem Patienten in der histopathologischen Untersuchung bestimmt werden . Schlussfolgerung : Die Verwendung von Goldmarkern bei Patienten mit Rektumkarzinom ermöglicht eine präzisere Definition der Zielvolumens für die Bestrahlungsplanung . Dadurch könnten evtl . anale Strukturen bei einer Tumorlage von ≥ 5 cm kranial des Analsphinkters geschont werden . Die Implantation von Goldmarkern verbessert die Kommunikation zwischen Chirurgen , Radioonkologen und Pathologen , was in einem intensivierten Austausch relevanter Informationen result iert Purpose To compare target dose distribution , comformality , normal tissue avoidance , and irradiated body volume ( IBV ) in 3DCRT using classic anatomical l and marks ( c3DCRT ) , 3DCRT fitting the PTV ( f3DCRT ) , and intensity-modulated radiation therapy ( IMRT ) in patients with locally advanced rectal cancer ( 
    Output:
    
There was a strong relationship between rectal filling and mesorectal motion .
Current margin recipes may not apply to deformable structures .