***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: BACKGROUND We have previously demonstrated that fluorodeoxyglucose-positron emission tomography ( FDG-PET ) can assess extent of pathologic response of primary rectal cancer to preoperative chemoradiation . Our goal was to determine the prognostic significance of FDG-PET assessment of rectal cancer response to preoperative chemoradiation . STUDY DESIGN Fifteen patients with locally advanced primary rectal cancer ( clinical ly bulky or tethered , or ultrasound evidence of T3 - 4 disease , N1 disease , or both ) deemed eligible for preoperative radiation and 5-FU-based chemotherapy ( 5,040 cGy to the pelvis and 2 cycles of bolus 5-FU/leucovorin ) were prospect ively enrolled from May 1997 to September 1998 .  FDG-PET was performed before and 4 to 5 weeks after completion of preoperative chemoradiation . FDG-PET parameters included maximum st and ard uptake value ( SUV(max ) ) , total lesion glycolysis ( TLG ) , and visual response score . Patients were prospect ively followed after operation , and disease status was determined . RESULTS All patients demonstrated some degree of response to preoperative therapy based on pathologic examination . At a median followup of 42 months ( range 23 to 54 months ) , 11 patients had no evidence of disease and 4 had died of disease . The mean percentage decrease in SUV(max ) ( DeltaSUV(max ) ) was 69 % for patients free from recurrence and 37 % for patients with recurrence ( p = 0.004 ) . DeltaSUV(max ) > or= 62.5 and deltaTLG > or= 69.5 were the best predictors of no- evidence -of-disease status and freedom from recurrence . Patients with DeltaSUV(max ) > or= 62.5 and deltaTLG > or= 69.5 had significantly improved disease-specific and recurrence-free survival ( p = 0.08 , 0.02 and p = 0.03 , 0.01 , respectively ) . CONCLUSIONS Our results indicate that FDG-PET assessment of locally-advanced rectal cancer response to preoperative chemoradiation may predict longterm outcomes PURPOSE Changes in F-18 fluorodeoxyglucose ( FDG ) uptake in normal tissues after chemoradiation therapy ( CRT ) potentially limit the ability of positron emission tomography ( PET ) to provide early assessment of therapeutic response . This study evaluated whether such changes negatively impact interpretation of posttherapy PET performed within 6 weeks of CRT completion and before definitive surgery in patients with locally advanced rectal cancer . The positive predictive value ( PPV ) and specificity of post-CRT PET , read clinical ly , was determined in 63 consecutive rectal cancer patients who had undergone preoperative CRT . METHODS AND MATERIAL S A schema for identifying and scoring postradiation effects on PET was prospect ively defined and applied in a blinded manner . This was compared with initial clinical reporting of response . Histologic assessment of the operative specimens was used as the reference st and ard . Correlation between clinical proctitis during CRT and radiation changes on subsequent PET was also assessed . RESULTS Clinical reporting of post-CRT PET yielded a high PPV ( 94 % ; 95 % confidence interval , 89 - -100 % ) but may have been exaggerated by the low prevalence of complete tumor clearance ( 16 % ) . The specificity was 80 % with only two false-positive results . On blinded reading , significant post-CRT effects on PET were recorded in 4 of 63 patients ( 6 % 95 % confidence interval , 0 - 13 % ) , but pattern recognition converted both false-positive PET results to a complete metabolic response . Clinical CRT proctitis was not correlated with PET findings . CONCLUSION Postradiation effects do not appear to significantly compromise the interpretation of PET for therapeutic response assessment . The proposed PET pattern of response may further improve the specificity of PET In the management of rectal cancer after the combined therapy of the radiation and surgical operation , the evaluation of the prognosis is important . Although fluoro-18-deoxy glucose positron emission tomography ( FDG-PET ) is considered as a useful tool for evaluation of therapeutic effect of this cancer as well as the other cancers , however , there are few articles that clearly describe the appropriate procedure of the FDG-PET in order to obtain the best prognostic value . The purpose of the present study is to compare several variations of a semi-quantification method , the St and ardized Uptake Values ( SUV ) and to determine the most appropriate parameter for the prognostic prediction and to propose the quantitative guideline of the FDG-PET . Especially , the authors focused on the SUV after radiotherapy , which had not been considered as a key quantitative value , as it was rather taken as a mere indicator of the therapeutic ( radiotherapeutic ) effect , not a direct indicator of the prognosis for the cancer itself . Methods : Forty patients with rectal cancer in the lower rectal region underwent two series of FDG-PET study before and after pre-operative radiotherapy . Their SUVs were calculated from FDG-PET data and compared with the results of the long-term follow-up of the patients as well as with histopathological outcomes . Results : All 40 patients had high FDG uptake before radiotherapy . The mean value of SUV before radiotherapy  ( SUV1 ) was 7.6 . After radiotherapy , the mean value of SUV ( SUV2 ) decreased to 4.2 . There was a significant difference in SUV2 between the groups with and without recurrence ( p<0.05 ) , however , SUV1 or SUV ratio ( SUV2/SUV1 ) displayed no significant difference with the incidence of recurrence . Conclusion : SUV2 was considered to be a good prognostic indicator for long-term prognosis of rectal cancer patients .  SUV1 nor SUV ratio SUV2/SUV1 did not have the equivalent prognostic usefulness . Subsets of patients with SUV2 greater than 3.2 should be observed closely PURPOSE To quantify the influence of fluctuating blood glucose level ( BGLs ) and the timing of PET acquisition on PET-based predictions of the pathological treatment response in rectal cancer . MATERIAL AND METHODS Thirty patients , diagnosed with locally advanced-rectal-cancer ( LARC ) , were included in this prospect i ve study . Sequential FDG-PET-CT investigations were performed at four time points during and after pre-operative radiochemotherapy ( RCT ) . All PET- data were normalized for the BGL measured shortly before FDG injection . The metabolic treatment response of the tumor was correlated with the pathological treatment response . RESULTS During RCT , strong intra-patient BGL-fluctuations were observed , ranging from -38.7 to 95.6 % . BGL-normalization of the SUVs revealed differences ranging from -54.7 to 34.7 % ( p < 0.001 ) . Also , a SUV(max ) time-dependency of 1.30 + /- 0.66 every 10 min ( range : 0.39 - 2.58 ) was found during the first 60 min of acquisition . When correlating the percent reduction of SUV(max ) after 2 weeks of RCT with the pathological treatment response , a significant increase ( p = 0.027 ) in the area under the curve of ROC-curve analysis was found when normalizing the PET- data for the measured BGLs , indicating an increase of the predictive strength . CONCLUSIONS This study strongly underlines the necessity of BGL-normalization of PET- data and a precise time-management between FDG injection and the start of PET acquisition when using sequential FDG-PET-CT imaging for the prediction of pathological treatment response UNLABELLED 18F-FDG PET is a useful tool for assessing the effects of chemo- or radiotherapy . The aim of this study was to correlate the change in tumor 18F-FDG st and ardized uptake value ( SUV ) during and after preoperative radiochemotherapy , with the pathologic response achieved in locally advanced rectal cancer ( LARC ) patients . METHODS Thirty-three patients with LARC underwent total mesorectal excision after preoperative treatment , including 3 cycles of oxaliplatin , raltitrexed , 5-fluorouracil , and folinic acid during pelvic radiotherapy ( 45 Gy ) . Staging procedures included endoscopic ultrasound , MRI , and CT . 18F-FDG PET scans were performed at baseline and 12 d after starting radiochemotherapy ( intermediate ) in all patients . Seventeen patients also had a presurgical scan . For each scan , mean and maximum SUVs were measured . The percentages of SUV decrease from baseline to intermediate ( early change ) and to presurgical scan ( overall change ) were assessed and correlated with pathologic response classified as tumor regression grade ( TRG ) . RESULTS Eighteen tumors ( 55 % ) showed complete ( TRG1 ) or subtotal regression ( TRG2 ) and were classified as responders , whereas 15 cases ( 45 % ; TRG3 or TRG4 ) were considered nonresponders . The early median decrease of tumor SUV significantly differed between responders ( -62 % ; range , -44 % to -100 % ) and nonresponders ( -22 % ; range , -2 % to -48 % ) . A significant correlation was also found between TRGs and early SUV changes ( P < 0.0001 ) . Responders were identified correctly by an early decrease of the mean SUV of > or = 52 % . CONCLUSION This study shows that early 18F-FDG PET can predict pathologic response to preoperative treatment . These findings support the usefulness of (18)F-FDG PET during the management with radiochemotherapy of LARC patients Accurate response assessment after neoadjuvant therapy is essential in patients with rectal cancer . The aim of this study was to assess the value of fluorine-18 fluorodeoxyglucose positron emission tomography ( FDG-PET ) in predicting response of locally advanced rectal cancer to preoperative multimodal treatment . Twenty-two consecutive patients with locally advanced ( uT3/4 ) primary rectal cancer were entered in this prospect i ve pilot study . FDG-PET was performed before and after neoadjuvant radiochemotherapy ( RCT ) with combined regional hyperthermia ( RHT ) . Treatment consisted of external-beam radiotherapy ( 45 Gy ) , chemotherapy ( folinic acid and 5-fluorouracil ) and regional pelvic hyperthermia followed by curative tumour resection 6–8 weeks later . Semi-quantitative measurements ( SUV ) of tumour FDG uptake were made before and 2–4 weeks after completion of neoadjuvant treatment . Two patients who did not receive post-therapeutic restaging by FDG-PET were excluded from the analysis . Results were correlated with findings on endorectal ultrasound ( EUS , n=17 patients ) and histopathology . Histopathological evaluation of the resected tumour revealed complete response in one patient , partial response in 12 and stable disease in seven . SUV reduction in tumours was significantly greater in responders than in non-responders [ 60 % ( ±15 % ) vs 30 % ( ±18 % ) , P=0.003 , CI=95 % ) . Using a minimum post-therapeutic SUV reduction of 36 % to define response , FDG-PET revealed a sensitivity of 100 % ( EUS : 33 % ) and a specificity of 86 % ( EUS : 80 % ) in response prediction ; the corresponding positive and negative predictive values were 93 % ( EUS : 80 % ) and 100 % ( EUS : 33 % ) , respectively . FDG-PET results were statistically significant ( P<0.001 , CI=95 % ) . FDG-PET has great potential in the assessment of tumour response to neoadjuvant RCT in combination with RHT and is superior to EUS for this purpose PURPOSE To develop a positron emission tomography (PET)-based response prediction model to differentiate pathological responders from nonresponders . The predictive strength of the model was vali date d in a second patient group , treated and imaged identical to the patients on which the predictive model was based . METHODS AND MATERIAL S Fifty-one rectal cancer patients were prospect ively included in this study . All patients underwent fluorodeoxyglucose ( FDG ) PET-computed tomography ( CT ) imaging both before the start of chemoradiotherapy ( CRT ) and after 2 weeks of treatment . Preoperative treatment with CRT was followed by a total mesorectal excision . From the resected specimen , the tumor regression grade ( TRG ) was scored according to the M and ard criteria . From one patient group ( n = 30 ) , the metabolic treatment response was correlated with the pathological treatment response , result ing in a receiver operating characteristic ( ROC ) curve based cutoff value for the reduction of maximum st and ardized uptake value ( SUV(max ) ) within the tumor to differentiate pathological responders ( TRG 1 - 2 ) from nonresponders ( TRG 3 - 5 ) . The applicability of the selected cutoff value for new patients was vali date d in a second patient group ( n = 21 ) . RESULTS When correlating the metabolic and pathological treatment response for the first patient group using ROC curve analysis ( area under the curve = 0.98 ) , a cutoff value of 48 % SUV(max ) reduction was selected to differentiate pathological responders from nonresponders ( specificity of 100 % , sensitivity of 6 
    Output:
    
Based on the subgroup analyses , there was no significant difference between the response index , the st and ardized uptake value and the visual response score in predicting the therapy response .
Therefore , FDG-PET is valuable for predicting the response of rectal carcinoma to neo-adjuvant therapy , and early evaluation of response during the therapy may be more promising .