***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 A pathologic complete response ( pCR ; ypT0N0 ) of a rectal tumor after neoadjuvant radiochemotherapy ( RCT )  is associated with an excellent prognosis . Several retrospective studies have investigated the effect of increasing the delay after RCT . The aim of this study was to evaluate the effect of increasing the interval between the end of RCT and surgery on the pCR rate . Methods GRECCAR6 was a phase III , multicenter , r and omized , open-label , parallel-group controlled trial . Patients with cT3/T4 or Tx N+ tumors of the mid or lower rectum who had received RCT ( 45 to 50 Gy with fluorouracil or capecitabine ) were included . Patients were r and omly included in the 7-week or the 11-week ( 11w ) group . Primary end point was the pCR rate defined as a ypT0N0 specimen ( NCT01648894 ) . Results A total of 265 patients from 24 centers were enrolled between October 2012 and February 2015 . The majority of the tumors were cT3 ( 82 % ) . After RCT , surgery was not performed in nine patients ( 3.4 % ) because of the occurrence of distant metastasis ( n = 5 ) or other reasons . Two patients underwent local resection of the tumor scar . A total of 47 ( 18.6 % ) specimens were classified as ypT0 ( four had invaded lymph nodes [ 8.5 % ] ) . The primary end point ( ypT0N0 ) was not different ( 7 weeks : 20 of 133 , 15.0 % v 11w : 23 of 132 , 17.4 % ; P = .5983 ) . Morbidity was significantly increased in the 11w group ( 44.5 % v 32 % ; P = .0404 ) as a result of increased medical complications ( 32.8 % v 19.2 % ; P = .0137 ) . The 11w group had a worse quality of mesorectal resection ( complete mesorectum [ I ] 78.7 % v 90 % ; P = .0156 ) . Conclusion Waiting 11 weeks after RCT did not increase the rate of pCR after surgical resection . A longer waiting period may be associated with higher morbidity and more difficult surgical resection BACKGROUND Organ preservation is a concept proposed for patients with rectal cancer after a good clinical response to neoadjuvant chemotherapy  , to potentially avoid morbidity and side-effects of rectal excision . The objective of this study was to compare local excision and total mesorectal excision in patients with a good response after chemoradiotherapy for lower rectal cancer . METHODS We did a prospect i ve , r and omised , open-label , multicentre , phase 3 trial at 15 tertiary centres in France that were experts in the treatment of rectal cancer . Patients aged 18 years and older with stage T2T3 lower rectal carcinoma , of maximum size 4 cm , who had a good clinical response to neoadjuvant chemoradiotherapy ( residual tumour ≤2 cm ) were central ly r and omly assigned by the surgeon before surgery to either local excision or total mesorectal excision surgery . R and omisation , which was done via the internet , was not stratified and used permuted blocks of size eight . In the local excision group , a completion total mesorectal excision was required if tumour stage was ypT2 - 3 . The primary endpoint was a composite outcome of death , recurrence , morbidity , and side-effects at 2 years after surgery , to show superiority of local excision over total mesorectal excision in the modified intention-to-treat ( ITT ) population ( expected proportions of patients having at least one event were 25 % vs 60 % for superiority ) . This trial was registered with Clinical Trials.gov , number NCT00427375 . FINDINGS From March 1 , 2007 , to Sept 24 , 2012 , 186 patients received chemoradiotherapy and were enrolled in the study . 148 good clinical responders were r and omly assigned to treatment , three were excluded ( because they had metastatic disease , tumour > 8 cm from anal verge , and withdrew consent ) , and 145 were analysed : 74 in the local excision group and 71 in the total mesorectal excision group . In the local excision group , 26 patients had a completion total mesorectal excision . At 2 years in the modified ITT population , one or more events from the composite primary outcome occurred in 41 ( 56 % ) of 73 patients in the local excision group and 33 ( 48 % ) of 69 in the total mesorectal excision group ( odds ratio 1·33 , 95 % CI 0·62 - 2·86 ; p=0·43 ) . In the modified ITT analysis , there was no difference between the groups in all components of the composite outcome , and superiority was not shown for local excision over total mesorectal excision . INTERPRETATION We failed to show superiority of local excision over total mesorectal excision , because many patients in the local excision group received a completion total mesorectal excision that probably increased morbidity and side-effects , and compromised the potential advantages of local excision . Better patient selection to avoid unnecessary completion total mesorectal excision could improve the strategy . FUNDING National Cancer Institute of France , Sanofi , Roche Pharma Purpose To study the predictive and prognostic value of magnetic resonance imaging (MRI)–assessed tumor response after long-course neoadjuvant therapy for locally advanced rectal cancer . Methods This study included 79 patients who had T3 or T4 and /or N+ rectal cancer treated with long-course neoadjuvant chemoradiation . MRI-assessed tumor regression grade ( mrTRG ) was assessed in 64 patients .  MRIs were review ed by the study radiologist . Surgical and pathologic reports for those who underwent surgery were review ed . Disease-free survival ( DFS ) was estimated . Progression during therapy , local relapse , metastasis , and death result ing from the tumor were classified as events . Statistical significance was calculated . Results In 11 patients , the tumor completely disappeared on MRI ; that is , it had an mrTRG of 1 . All but one patient , who chose deferred surgery , had a complete pathologic response ( pCR ) , with a positive predictive value of nearly 100 % . Of the 20 patients who had an mrTRG of 2 on MRI , six had a pCR . mrTRG 3 , mrTRG 4 , and mrTRG 5 were detected in 24 , six , and three patients , respectively , of whom only one patient had a pCR . The 2-year DFS was 77 % . The mrTRG was significant for DFS . The 2-year DFS was 88 % for patients with a good response versus 66 % for those with a poor response ( P = .046 ) . Conclusion MRI-assessed complete tumor response was strongly correlated with pCR and , therefore , can be used as a surrogate marker to predict absence of viable tumor cells . Our results can be used to implement use of mrTRGs in larger prospect i ve correlative studies as a tool to select patients for whom deferred surgery may be appropriate . Also , those with a poor response may be offered further treatment options before definitive surgery OBJECTIVE The purpose of this study was to evaluate the prognostic relevance of a modified 3-point MRI-based tumor regression grading system incorporating DWI for patients with locally advanced rectal cancer after preoperative chemoradiotherapy ( CRT ) . MATERIAL S AND METHODS Between March 2012 and September 2013 , 118 consecutively registered patients with middle or lower locally advanced rectal cancer who underwent CRT followed by surgery  were enrolled in this retrospective study . Two radiologists in consensus assessed MRI tumor regression grade ( mrTRG ) based on T2-weighted images and high b value DW images ( 0 and 1000 s/mm2 ) using the following grade s : 0 , complete regression ( no obvious tumor ) ; 1 , intermediate regression ( dominant fibrosis , regression > 50 % ) ; 2 , poor regression ( dominant tumor , regression ≤ 50 % ) . Multivariate analysis with a Cox regression model was performed to evaluate the association between modified mrTRG and 3-year disease-free survival ( DFS ) rate . A Kaplan-Meier method with a log-rank test was used to compare the DFS rate between responder ( grade s 0 and 1 ) and nonresponder ( grade 2 ) groups . RESULTS Both the accuracy ( 72.9 % vs 38.1 % ; p < 0.001 ) and the interreader agreement ( κ = 0.580 vs 0.338 ; p < 0.001 ) of modified 3-point mrTRG were improved over the established 5-point mrTRG . Modified mrTRG ( adjusted hazard ratio , 2.505 ; 95 % CI , 1.231 - 5.100 ) was independently associated with 3-year DFS rate ( p = 0.011 ) . There was also a significant difference in the 3-year DFS rate between responders ( 73.8 % ; 95 % CI , 64.2 - 81.3 % ) and nonresponders ( 41.7 % ; 95 % CI , 10.9 - 70.8 % ) ( p = 0.028 ) . CONCLUSION In patients with middle or lower locally advanced rectal cancer , the modified 3-point mrTRG incorporating DWI was independently associated with the 3-year DFS rate after CRT followed by surgery . The grading scale may be used as a surrogate for expected prognosis of preoperative CRT . Further prospect i ve trials are warranted Introduction : Nonoperative management ( NOM ) of rectal cancer after a complete clinical response ( cCR ) to neoadjuvant therapy is controversial . In this article , we retrospectively review ed the outcomes of patients managed with selective NOM after a cCR to neoadjuvant treatment  and compared these with patients who underwent st and ard rectal resection with a pathological complete response ( pCR ) . Methods : Patients completing neoadjuvant chemoradiotherapy ( CRT ) for stage I to III rectal cancer between January 2006 and August 2010 were retrospectively review ed .  Median follow-up was calculated in months after completion of CRT . Results : Thirty-two patients ( median follow-up 28 months ) were treated by NOM after a cCR . Among 265 treated by CRT and rectal resection  , 57 patients ( 22 % ) had a pCR and formed the control group ( median follow-up 43 months ) . Factors associated with selective use of NOM included lower pretreatment stage , older age , and distal tumor location ( P < 0.05 ) . In the NOM group , 6 recurred locally ( median 11 months , range 7–14 ) , 3 of whom also had concurrent distant recurrence . All 6 local failures were controlled by salvage rectal resection with no further local recurrence of disease ( median follow-up 17 months ) . In the rectal resection/pCR group , there were no local failures . The 2-year distant disease-free survival ( 88 % vs 98 % , P = 0.27 ) and overall survival ( 96 % vs 100 % , P = 0.56 ) were similar for NOM and rectal resection/pCR groups . Conclusions : Rectal resection was successfully avoided in 81 % of patients selected for NOM . When combined with salvage surgery , NOM appears to achieve similar local and distant disease control compared with patients with a pCR treated by rectal resection . Longer follow-up and prospect i ve trials are warranted to evaluate this promising treatment option PURPOSE To retrospectively assess accuracy of magnetic resonance ( MR ) imaging after radiation therapy with concomitant chemotherapy for downsizing of the primary lesion to ypT0 - 2 tumor confined to rectal wall in locally advanced rectal cancer , with histopathologic findings as reference st and ard , and to evaluate additional value of volumetric analysis . MATERIAL S AND METHODS The institutional review board approved the study and waived informed consent . Sixty-seven patients met criteria of the study .  T2-weighted MR images obtained before and after radiation therapy with concomitant chemotherapy were assessed for tumor stage by expert abdominal radiologist , colorectal surgeon , and general radiologist . Sensitivity , specificity , positive predictive value ( PPV ) , and negative predictive value ( NPV ) were calculated ; tumor volume was measured ( compared with Mann-Whitney U test ) . Findings were correlated with histopathologic findings . RESULTS Sixty-seven patients ( 38 men , 29 women ; mean age , 63 years ) who underwent radiation therapy with concomitant chemotherapy and surgery ( all but one ) were evaluated . The PPV for prediction of tumor confined to rectal wall ( ypT0 - 2 ) was 91 % ( 10 of 11 ) , 86 % ( six of seven ) , and 88 % ( seven of eight ) for expert abdominal radiologist , surgeon , and general radiologist , respectively . In 24 patients , sensitivity was 42 % ( 10 ) , 25 % ( six ) , and 29 % ( seven ) . ypT0 - 2 tumors had significantly smaller volumes than did ypT3 - 4 tumors before radiation therapy with concomitant chemotherapy ( 55 vs 92 cm(3 ) , P = .038 ) 
    Output:
    
mrTRG 1 showed high specificity for pCR and ≤ypT1 , but suboptimal sensitivity .
mrTRG 1 or 2 showed higher sensitivity for pCR and ≤ypT1 , but lower specificity .
Because of the suboptimal sensitivity of mrTRG 1 , it might be limited as a criterion for less aggressive treatment after neoadjuvant chemoradiotherapy . •
Magnetic resonance tumor regression grade 1 shows high specificity for pCR and ≤ypT1 , but suboptimal sensitivity . •
Magnetic resonance tumor regression grade 1 or 2 shows higher sensitivity for pCR and ≤ypT1 , but lower specificity than magnetic resonance tumor regression grade 1 alone