***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 assess prospect ively the prognostic value of FDG PET/CT during curative-intent radiotherapy ( RT ) with or without concomitant chemotherapy in patients with non-small-cell lung cancer ( NSCLC ) . Methods Patients with histological proof of invasive localized NSCLC and evaluable tumour , and who were c and i date s for curative-intent radiochemotherapy ( RCT ) or RT were preincluded after providing written informed consent . Definitive inclusion was conditional upon significant FDG uptake before RT ( PET1 ) . All included patients had a FDG PET/CT scan during RT ( PET2 , mean dose 43 Gy ) and were evaluated by FDG PET/CT at 3 months and 1 year after RT . The main endpoint was death ( from whatever cause ) or tumour progression at 1 year . Results Of 77 patients preincluded , 52 were evaluable . Among the evaluable patients , 77 % received RT with induction chemotherapy and 73 % RT with concomitant chemotherapy . At 1 year , 40 patients ( 77 % ) had died or had tumour progression . No statistically significant association was found between stage ( IIIB vs. other ) , histology ( squamous cell carcinoma vs. other ) , induction or concomitant chemotherapy , and death/tumour progression at 1 year . The SUVmax in the PET2 scan was the single variable predictive of death or tumour progression at 1 year ( odds ratio 1.97 , 95 % CI 1.25 – 3.09 , p = 0.003 ) in multivariate analysis . The area under the receiver operating characteristic curve was 0.85 ( 95 % CI 0.73 – 0.94 , p < 10−4 ) . A SUVmax value of 5.3 in the PET2 scan yielded a sensitivity of 70 % and a specificity of 92 % for predicting tumour progression or death at 1 year . Conclusion This prospect i ve multicentre study demonstrated the prognostic value in terms of disease-free survival of SUVmax assessed during the 5th week of curative-intent RT or RCT in NSCLC patients ( NCT01261598 ; RTEP2 study ) The potential of 18F-FDG PET changes was evaluated for prediction of response to concomitant chemoradiotherapy in patients with locally advanced non – small cell lung cancer ( NSCLC ) . Methods : For 28 patients , 18F-FDG PET was performed before treatment , at the end of the second week of treatment , and at 2 wk and 3 mo after the completion of treatment . St and ardized uptake value ( SUV ) , maximum SUV , metabolic tumor volume ( MTV ) , and total lesion glycolysis ( TLG ) were obtained . Early metabolic changes were defined as fractional change ( ΔTLG ) when 18F-FDG PET at the end of the second week was compared with pretreatment 18F-FDG PET . In-treatment metabolic changes , as measured by serial 18F-FDG PET , were correlated with st and ard criteria of response evaluation of solid tumors by means of CT imaging ( Response Evaluation Criteria In Solid Tumors 1.1 ) . Parameters were analyzed for stratification in progression-free survival ( PFS ) . Results : When compared with early metabolic nonresponders , a ΔTLG decrease of 38 % or more was associated with a significantly longer PFS ( 1-y PFS 80 % vs. 36 % , P = 0.02 ) . Pretreatment TLG was found to be a prognostic factor for PFS . Conclusion : The degree of change in TLG was predictive for response to concomitant chemoradiotherapy as early as the end of the second week into treatment for patients with locally advanced NSCLC . Pretreatment TLG was prognostic for PFS OBJECTIVES The objectives were ( i ) to confirm that diagnostic FDG-PET images could be obtained during thoracic radiotherapy , ( ii ) to verify that significant changes in FDG uptake or volume could be measured early enough to adapt the radiotherapy plan and ( iii ) to determine an optimal time window during the radiotherapy course to acquire a single FDG-PET examination that would be representative of tumour response . METHODS Ten non-small cell lung carcinoma ( NSCLC ) patients with significant PET/CT-FDG tumour radioactivity uptake ( versus the background level ) , c and i date s for curative radiotherapy ( RT , n=4 ; 60 - 70 Gy , 2 Gray per fraction , 5 fractions per week ) or RT plus chemotherapy ( CT-RT , n=6 ) , were prospect ively evaluated . Using a Siemens Biograph , 5 or 6 PET/CT scans ( PET(n ) , n=0 - 5 ) were performed for each patient . Each acquisition included a 15-min thoracic PET with respiratory gating ( RG ) 60±5 min post-injection of the FDG ( 3.5 MBq/kg ) , followed by a st and ard , 5-min non-gated ( STD ) thoracic PET . PET(0 ) was performed before the first RT fraction . During RT , PET(1 - 5 ) were performed every 7 fractions , i.e. , at 14 Gy total dose increment . FDG uptake was measured as the variation of SUV(max , PETn ) versus SUV(max , PET0 ) . Each lesions ' volume was measured by ( i ) visual delineation by an experienced nuclear physician , ( ii ) 40 % SUV(max ) fixed threshold and ( iii ) a semi-automatic adaptive threshold method . RESULTS A total of 53 FDG-PET scans were acquired . Seventeen lesions ( 6 tumours and 11 nodes ) were visible on PET(0 ) in the 10 patients . The lesions were located either in or near the mediastinum or in the apex , without significant respiratory displacements at visual inspection of the gated images . Healthy lung did not cause motion artefacts in the PET images . As measured on 89 lesions , both the absolute and relative SUV(max ) values decreased as the RT dose increased . A 50 % SUV(max ) decrease was obtained around a total dose of 45 Gy . Out of the 89 lesions , 75 remained visually identifiable during the entire course of treatment . The 40 % fixed threshold and adaptive threshold methods failed to delineate otherwise visible lesions in 16/33 ( 48 % ) and 3/33 ( 9 % ) lesions , respectively . The failure rate increased with increasing RT doses . Restricting the analysis to the manually-defined volumes in 89 visible lesions , the relative volumes decreased with increased dose . CONCLUSIONS FDG-PET images can be analysed during thoracic RT , given either alone or with chemotherapy , without disturbing radiation-induced artefacts . An average 50 % decrease in SUV(max ) was observed around 40 - 45 Gy ( i.e. , during week 5 of RT ) . The three delineation methods yielded consistent volume measurements before RT and during the first week of RT , while manual delineation appeared to be more reliable later on during RT The objectives of this study were to investigate the relationship between CT- and 18F-FDG PET – based tumor volumes in non – small cell lung cancer ( NSCLC ) and the impact of tumor size and uptake heterogeneity on various approaches to delineating uptake on PET images . Methods : Twenty-five NSCLC cancer patients with 18F-FDG PET/CT were considered . Seventeen underwent surgical resection of their tumor , and the maximum diameter was measured . Two observers manually delineated the tumors on the CT images and the tumor uptake on the corresponding PET images , using a fixed threshold at 50 % of the maximum ( T50 ) , an adaptive threshold methodology , and the fuzzy locally adaptive Bayesian ( FLAB ) algorithm . Maximum diameters of the delineated volumes were compared with the histopathology reference when available . The volumes of the tumors were compared , and correlations between the anatomic volume and PET uptake heterogeneity and the differences between delineations were investigated . Results : All maximum diameters measured on PET and CT images significantly correlated with the histopathology reference ( r > 0.89 , P < 0.0001 ) . Significant differences were observed among the approaches : CT delineation result ed in large overestimation ( + 32 % ± 37 % ) , whereas all delineations on PET images result ed in underestimation ( from −15 % ± 17 % for T50 to −4 % ± 8 % for FLAB ) except manual delineation ( + 8 % ± 17 % ) . Overall , CT volumes were significantly larger than PET volumes ( 55 ± 74 cm3 for CT vs. from 18 ± 25 to 47 ± 76 cm3 for PET ) . A significant correlation was found between anatomic tumor size and heterogeneity ( larger lesions were more heterogeneous ) . Finally , the more heterogeneous the tumor uptake , the larger was the underestimation of PET volumes by threshold-based techniques . Conclusion : Volumes based on CT images were larger than those based on PET images . Tumor size and tracer uptake heterogeneity have an impact on threshold-based methods , which should not be used for the delineation of cases of large heterogeneous NSCLC , as these methods tend to largely underestimate the spatial extent of the functional tumor in such cases . For an accurate delineation of PET volumes in NSCLC , advanced image segmentation algorithms able to deal with tracer uptake heterogeneity should be preferred Background We studied whether maximum st and ardized uptake values ( SUV ) from [ 18 F ] PET/CT predict clinical outcome after concurrent proton/chemotherapy for stage III non-small cell lung cancer ( NSCLC ) . Methods Eighty-four patients were treated prospect ively with 74 Gy(RBE ) proton therapy and concurrent chemotherapy . PET/CT scans were available before ( SUV1 ) and within 6 months after ( SUV2 ) treatment . The predictive value of clinical and PET/CT factors were analyzed with univariate and multivariate Cox regression models . Results Median survival time was 29.9 months . At 3 years , the local recurrence-free survival ( LRFS ) rate was 34.8 % ; distant metastasis-free survival ( DMFS ) , 35.4 % ; progression-free survival ( PFS ) , 31.2 % ; and overall survival ( OS ) , 37.2 % . Patients with SUV2 ≥3.6 ( the median ) had high rates of LR ( p = 0.021 ) . Of 12 clinicopathologic features evaluated in univariate analysis , only KPS , SUV1 , and SUV2 predicted LRFS , DMFS , PFS , and OS ( p < 0.05 ) . Multivariate analysis showed that KPS ( p = 0.025 ) and SUV2 ( p = 0.017 ) were independently prognostic for LRFS and that SUV1 , SUV2 , and KPS were independently prognostic for DMFS , PFS , and OS ( p < 0.05 ) . Conclusions SUV2 predicted LRFS , and SUV1 and SUV2 predicted DMFS , PFS , and OS , in patients with stage III NSCLC treated with concurrent chemotherapy and high-dose proton therapy 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 64 % ) . Applying this cutoff value to the second patient group result ed in a specificity and sensitivity of , respectively , 93 % and 83 % , with only one of the pathological nonresponders being false positively predicted as pathological responding . CONCLUSIONS For rectal cancer , an accurate PET-based prediction of the pathological treatment response is feasible already after 2 weeks of CRT . The presented predictive model could be used to select patients to be considered for less invasive surgical interventions or even a " wait and see " policy . Also , based on the predicted response , early modifications of the treatment protocol are possible , which might result in an improved clinical outcome PURPOSE In this prospect i ve National Cancer Institute-funded American College of Radiology Imaging Network/Radiation Therapy Oncology Group cooperative group trial , we hypothesized that st and ard 
    Output:
    
Conclusion Certainly , the lack of univocal PET parameters was identified as a major drawback , while st and ardization would be required for best practice .
In any case , all these papers denoted FDGint as promising and a challenging examination for early assessment of outcomes during CRT , sustaining its predictivity in lung cancer