Accurate prediction of pathological rectal tumor response after two weeks of preoperative radiochemotherapy using (18)F-fluorodeoxyglucose-positron emission tomography-computed tomography imaging

Adaptive Individualized high-dose preoperAtive (AIDA) chemoradiation in high-risk rectal cancer: a phase II trial

PURPOSE

To evaluate the pathological complete response (pCR) rate of locally advanced rectal cancer (LARC) after adaptive high-dose neoadjuvant chemoradiation (CRT) based on 18 F-fluorodeoxyglucose positron emission tomography/computed tomography (18 F-FDG-PET/CT).

METHODS

The primary endpoint was the pCR rate. Secondary endpoints were the predictive value of 18 F-FDG-PET/CT on pathological response and acute and late toxicity. All patients performed 18 F-FDG-PET/CT at baseline (PET0) and after 2 weeks during CRT (PET1). The metabolic PET parameters were calculated both at the PET0 and PET1. The total CRT dose was 45 Gy to the pelvic lymph nodes and 50 Gy to the primary tumor, corresponding mesorectum, and to metastatic lymph nodes. Furthermore, a sequential boost was delivered to a biological target volume defined by PET1 with an additional dose of 5 Gy in 2 fractions. Capecitabine (825 mg/m2 twice daily orally) was prescribed for the entire treatment duration.

RESULTS

Eighteen patients (13 males, 5 females; median age 55 years [range, 41-77 years]) were enrolled in the trial. Patients underwent surgical resection at 8-9 weeks after the end of neoadjuvant CRT. No patient showed grade > 1 acute radiation-induced toxicity. Seven patients (38.8%) had TRG = 0 (complete regression), 5 (27.0%) showed TRG = 2, and 6 (33.0%) had TRG = 3. Based on the TRG results, patients were classified in two groups: TRG = 0 (pCR) and TRG = 1, 2, 3 (non pCR). Accepting p < 0.05 as the level of significance, at the Kruskal-Wallis test, the medians of baseline-MTV, interim-SUVmax, interim-SUVmean, interim-MTV, interim-TLG, and the MTV reduction were significantly different between the two groups. 18 F-FDG-PET/CT was able to predict the pCR in 77.8% of cases through compared evaluation of both baseline PET/CT and interim PET/CT.

CONCLUSIONS

Our results showed that a dose escalation on a reduced target in the final phase of CRT is well tolerated and able to provide a high pCR rate.

Impact of preoperative chemoradiation with higher dose intensity modulated radiotherapy on pathological complete response for locally advanced rectal cancer: a systematic review

INTRODUCTION

Neoadjuvant chemoradiation (CRT) followed by total mesorectal excision is the current standard-of-care for locally advanced UICC II-III stage rectal cancer (LARC). A pathological complete response (pCR) correlates with survival. Improvements of pCR, including dose escalation, should be explored. The aim of this explorative analysis is to assess the impact on pCR of intensity-modulated radiotherapy (IMRT) with simultaneous integrated boost (SIB).

AREAS COVERED

A literature search via PICO (Population, Intervention, Comparison, Outcome) in MEDLINE/PubMed and EMBASE and a systematic review according to PRISMA (Preferred Reporting Items for Systematic Reviews and Metanalysis) methodology were performed. Studies that reported pCR rate in patients with LARC in clinical stage T2N+M0 or cT3/4 N0/+M0 treated with preoperative CRT with SIB-IMRT/VMAT (Volumetric Modulated Arc Therapy) were included. Sixty-two studies were identified, but only eight clinical trials with a total of 311 patients were included . Median follow-up was 16-61 months. pCR reached the value of 38%. Good survival outcomes were observed with a mild toxicity profile.

EXPERT OPINION

Radiotherapy dose intensification in LARC showed a slight increase of pCR compared to historical studies. Prospective evaluations are necessary to define which patients would benefit most.

Predicting neoadjuvant chemoradiotherapy response with functional imaging and liquid biomarkers in locally advanced rectal cancer

INTRODUCTION

Non-invasive predictive quantitative biomarkers are required to guide treatment individualization in patients with locally advanced rectal cancer (LARC) in order to maximise therapeutic outcomes and minimise treatment toxicity. Magnetic resonance imaging (MRI), positron emission tomography (PET) and blood biomarkers have the potential to predict chemoradiotherapy (CRT) response in LARC.

AREAS COVERED

This review examines the value of functional imaging (MRI and PET) and liquid biomarkers (circulating tumor cells (CTCs) and circulating tumor nucleic acid (ctNA)) in the prediction of CRT response in LARC. Selected imaging and liquid biomarker studies are presented and the current status of the most promising imaging (apparent diffusion co-efficient (ADC), K^trans, SUV_max, metabolic tumor volume (MTV) and total lesion glycolysis (TLG) and liquid biomarkers (circulating tumor cells (CTCs), circulating tumor nucleic acid (ctNA)) is discussed. The potential applications of imaging and liquid biomarkers for treatment stratification and a pathway to clinical translation are presented.

EXPERT OPINION

Functional imaging and liquid biomarkers provide novel ways of predicting CRT response. The clinical and technical validation of the most promising imaging and liquid biopsy biomarkers in multi-centre studies with harmonised acquisition techniques is required. This will enable clinical trials to investigate treatment escalation or de-escalation pathways in rectal cancer.

Multi-modal radiomics model to predict treatment response to neoadjuvant chemotherapy for locally advanced rectal cancer

BACKGROUND

Neoadjuvant chemotherapy is currently recommended as preoperative treatment for locally advanced rectal cancer (LARC); however, evaluation of treatment response to neoadjuvant chemotherapy is still challenging.

AIM

To create a multi-modal radiomics model to assess therapeutic response after neoadjuvant chemotherapy for LARC.

METHODS

This retrospective study consecutively included 118 patients with LARC who underwent both computed tomography (CT) and magnetic resonance imaging (MRI) before neoadjuvant chemotherapy between October 2016 and June 2019. Histopathological findings were used as the reference standard for pathological response. Patients were randomly divided into a training set (n = 70) and a validation set (n = 48). The performance of different models based on CT and MRI, including apparent diffusion coefficient (ADC), dynamic contrast enhanced T1 images (DCE-T1), high resolution T2-weighted imaging (HR-T2WI), and imaging features, was assessed by using the receiver operating characteristic curve analysis. This was demonstrated as area under the curve (AUC) and accuracy (ACC). Calibration plots with Hosmer-Lemeshow tests were used to investigate the agreement and performance characteristics of the nomogram.

RESULTS

Eighty out of 118 patients (68%) achieved a pathological response. For an individual radiomics model, HR-T2WI performed better (AUC = 0.859, ACC = 0.896) than CT (AUC = 0.766, ACC = 0.792), DCE-T1 (AUC = 0.812, ACC = 0.854), and ADC (AUC = 0.828, ACC = 0.833) in the validation set. The imaging performance for extramural venous invasion detection was relatively low in both the training (AUC = 0.73, ACC = 0.714) and validation (AUC = 0.578, ACC = 0.583) sets. The multi-modal radiomics model reached an AUC of 0.925 and ACC of 0.886 in the training set, and an AUC of 0.93 and ACC of 0.875 in the validation set. For the clinical radiomics nomogram, good agreement was found between the nomogram prediction and actual observation.

CONCLUSION

A multi-modal nomogram using traditional imaging features and radiomics of preoperative CT and MRI adds accuracy to the prediction of treatment outcome, and thus contributes to the personalized selection of neoadjuvant chemotherapy for LARC.

Radiomics-Based Pretherapeutic Prediction of Non-response to Neoadjuvant Therapy in Locally Advanced Rectal Cancer

Objective

The aim of this study was to investigate whether pretherapeutic, multiparametric magnetic resonance imaging (MRI) radiomic features can be used for predicting non-response to neoadjuvant therapy in patients with locally advanced rectal cancer (LARC).

Methods

We retrospectively enrolled 425 patients with LARC [allocated in a 3:1 ratio to a primary (n = 318) or validation (n = 107) cohort] who received neoadjuvant therapy before surgery. All patients underwent T1-weighted, T2-weighted, diffusion-weighted, and contrast-enhanced T1-weighted MRI scans before receiving neoadjuvant therapy. We extracted 2424 radiomic features from the pretherapeutic, multiparametric MR images of each patient. The Wilcoxon rank-sum test, Spearman correlation analysis, and least absolute shrinkage and selection operator regression were successively performed for feature selection, whereupon a multiparametric MRI-based radiomic model was established by means of multivariate logistic regression analysis. This feature selection and multivariate logistic regression analysis was also performed on all single-modality MRI data to establish four single-modality radiomic models. The performance of the five radiomic models was evaluated by receiver operating characteristic (ROC) curve analysis in both cohorts.

Results

The multiparametric, MRI-based radiomic model based on 16 features showed good predictive performance in both the primary (p < 0.01) and validation (p < 0.05) cohorts, and performed better than all single-modality models. The area under the ROC curve of this multiparametric MRI-based radiomic model achieved a score of 0.822 (95% CI 0.752–0.891).

Conclusions

We demonstrated that pretherapeutic, multiparametric MRI radiomic features have potential in predicting non-response to neoadjuvant therapy in patients with LARC.

Electronic supplementary material

The online version of this article (10.1245/s10434-019-07300-3) contains supplementary material, which is available to authorized users.

Anal cancer chemoradiotherapy outcome prediction using 18F-fluorodeoxyglucose positron emission tomography and clinicopathological factors

OBJECTIVE

To assess the role of [¹⁸F]fluorodeoxyglucose (FDG) positron emission tomography (PET), obtained before and during chemoradiotherapy, in predicting locoregional failure relative to clinicopathological factors for patients with anal cancer.

METHODS

93 patients with anal squamous cell carcinoma treated with chemoradiotherapy were included in a prospective observational study (NCT01937780). FDG-PET/CT was performed for all patients before treatment, and for a subgroup (n = 39) also 2 weeks into treatment. FDG-PET was evaluated with standardized uptake values (SUV_{max/peak/mean}), metabolic tumor volume (MTV), total lesion glycolysis (TLG), and a proposed Z-normalized combination of MTV and SUV_peak (ZMP). The objective was to predict locoregional failure using FDG-PET, tumor and lymph node stage, gross tumor volume (GTV) and human papilloma virus (HPV) status in univariate and bivariate Cox regression analysis.

RESULTS

N3 lymph node stage, HPV negative tumor, GTV, MTV, TLG and ZMP were in univariate analysis significant predictors of locoregional failure (p < 0.01), while SUV_{max/peak/mean} were not (p > 0.2). In bivariate analysis HPV status was the most independent predictor in combinations with N3 stage, ZMP, TLG, and MTV (p < 0.02). The FDG-PET parameters at 2 weeks into radiotherapy decreased by 30-40 % of the initial values, but neither absolute nor relative decrease improved the prediction models.

CONCLUSION

Pre-treatment PET parameters are predictive of chemoradiotherapy outcome in anal cancer, although HPV negativity and N3 stage are the strongest single predictors. Predictions can be improved by combining HPV with PET parameters such as MTV, TLG or ZMP. PET 2 weeks into treatment does not provide added predictive value.

ADVANCES IN KNOWLEDGE

Pre-treatment PET parameters of anal cancer showed a predictive role independent of clinicopathological factors. Although the PET parameters show substantial reduction from pre- to mid-treatment, the changes were not predictive of chemoradiotherapy outcome.

Does baseline [18F] FDG-PET/CT correlate with tumor staging, response after neoadjuvant chemoradiotherapy, and prognosis in patients with rectal cancer?

BACKGROUND

[18F] fluorodeoxyglucose positron emission tomography/computed tomography ([18F] FDG-PET/CT) may be used for tumor staging and prognosis in several tumors but its role in rectal cancer is still debated. The aim of the present study was to assess the correlation of baseline [18F] FDG-PET parameters with tumor staging, tumor response (tumor regression grade (TRG)), and outcome in a series of patients affected by locally advanced rectal cancer (LARC) treated with neoadjuvant chemoradiotherapy (CRT).

METHODS

One hundred patients treated with neoadjuvant CRT and radical surgery were enrolled in the present study. Maximum standardized uptake value (SUVmax), SUVmean, metabolic tumor volume (MTV), and total lesion glycolysis (TLG) at the baseline [18F] FDG-PET were calculated. These PET parameters were correlated with tumor staging, histopathological data (TRG1 vs. TRG2-5 and TRG1-2 vs. TRG3-5), disease-free survival, and overall survival.

RESULTS

SUVmax and SUVmean of primary tumor were statistically associated with T4-stage. SUVmax, SUVmean, and TLG did not result statistically associated with TRG (TRG1 or TRG1-2). MTV resulted statistically associated with TRG1-2 group (OR 2.9; 95% CI 1.2-7.1). Finally, no PET parameter was significantly associated with disease-free or overall survival.

CONCLUSION

Our results showed that baseline [18F] FDG-PET parameters correlated with tumor staging, and only MTV correlated with TRG 1-2. PET parameters failed to predict disease-free and overall survival after treatment completion. The results leave open to further studies the issue of identifying patients suitable for conservative approaches.

MRI-Based Apparent Diffusion Coefficient for Predicting Pathologic Response of Rectal Cancer After Neoadjuvant Therapy: Systematic Review and Meta-Analysis

OBJECTIVE

The purpose of this study was to assess the use of apparent diffusion coefficient (ADC) during DWI for predicting complete pathologic response of rectal cancer after neoadjuvant therapy.

MATERIALS AND METHODS

A systematic review of available literature was conducted to retrieve studies focused on the identification of complete pathologic response of locally advanced rectal cancer after neoadjuvant chemoradiation, through the assessment of ADC evaluated before, after, or both before and after treatment, as well as in terms of the difference between pretreatment and posttreatment ADC. Pooled mean pretreatment ADC, posttreatment ADC, and Δ-ADC (calculated as posttreatment ADC minus pretreatment ADC divided by pretreatment ADC and multiplied by 100) in complete responders versus incomplete responders were calculated. For each parameter, we also pooled sensitivity and specificity and calculated the area under the summary ROC curve.

RESULTS

We found 10 prospective and eight retrospective studies. Overall, pathologic complete response was observed in 22.2% of patients. Pooled mean pretreatment ADC in complete responders was 0.84 × 10^-3 mm²/s versus 0.89 × 10^-3 mm²/s in incomplete responders (p = 0.33). Posttreatment ADC values were 1.51 × 10^-3 mm²/s and 1.29 × 10^-3 mm²/s, in complete and incomplete responders, respectively (p = 0.00001). The Δ-ADC percentages were also significantly higher in complete responders than in incomplete responders (59.7% vs 29.7%, respectively, p = 0.016). Pooled sensitivity, specificity, and AUC were 0.743, 0.755, and 0.841 for pretreatment ADC; 0.800, 0.737, and 0.782 for posttreatment ADC; and 0.832, 0.806, and 0.895 for Δ-ADC.

CONCLUSION

Use of ADC during DWI is a promising technique for assessment of results of neoadjuvant treatment of rectal cancer.

Rectal cancer MRI: protocols, signs and future perspectives radiologists should consider in everyday clinical practice

Abstract

Magnetic resonance imaging (MRI) allows to non-invasively evaluate rectal cancer staging and to assess the presence of “prognostic signs” such as the distance from the anorectal junction, the mesorectal fascia infiltration and the extramural vascular invasion. Moreover, MRI plays a crucial role in the assessment of treatment response after chemo-radiation therapy, especially considering the growing interest in the new conservative policy (wait and see, minimally invasive surgery). We present a practical overview regarding the state of the art of the MRI protocol, the main signs that radiologists should consider for their reports during their clinical activity and future perspectives.

Teaching Points

• MRI protocol for rectal cancer staging and re-staging.

• MRI findings that radiologists should consider for reports during everyday clinical activity.

• Perspectives regarding the development of latest technologies.

Adaptive radiation dose escalation in rectal adenocarcinoma: a review

Total mesorectal excision (TME) after neoadjuvant chemoradiotherapy (CRT) has offered superior control for patients with locally advanced rectal cancer, but can carry a quality of life cost. Fortunately, some patients achieve a complete response after CRT alone without the added morbidity caused by surgery. Efforts to increase fidelity of radiation treatment planning and delivery may allow for escalated doses of radiotherapy (RT) with limited off-target toxicity and elicit more pathological complete responses (pCR) to CRT thereby sparing more rectal cancer patients from surgery. In this review, methods of delivering escalated RT boost above 45-50.4 Gy are discussed including: 3D conformal, intensity-modulated radiotherapy (IMRT), and brachytherapy. Newly developed adaptive boost strategies and imaging modalities used in RT planning and response evaluation such as magnetic resonance imaging (MRI) and positron emission tomography (PET) are also discussed.

Radiomics Analysis for Evaluation of Pathological Complete Response to Neoadjuvant Chemoradiotherapy in Locally Advanced Rectal Cancer

Purpose: To develop and validate a radiomics model for evaluating pathologic complete response (pCR) to neoadjuvant chemoradiotherapy in patients with locally advanced rectal cancer (LARC).Experimental Design: We enrolled 222 patients (152 in the primary cohort and 70 in the validation cohort) with clinicopathologically confirmed LARC who received chemoradiotherapy before surgery. All patients underwent T2-weighted and diffusion-weighted imaging before and after chemoradiotherapy; 2,252 radiomic features were extracted from each patient before and after treatment imaging. The two-sample t test and the least absolute shrinkage and selection operator regression were used for feature selection, whereupon a radiomics signature was built with support vector machines. Multivariable logistic regression analysis was then used to develop a radiomics model incorporating the radiomics signature and independent clinicopathologic risk factors. The performance of the radiomics model was assessed by its calibration, discrimination, and clinical usefulness with independent validation.Results: The radiomics signature comprised 30 selected features and showed good discrimination performance in both the primary and validation cohorts. The individualized radiomics model, which incorporated the radiomics signature and tumor length, also showed good discrimination, with an area under the receiver operating characteristic curve of 0.9756 (95% confidence interval, 0.9185-0.9711) in the validation cohort, and good calibration. Decision curve analysis confirmed the clinical utility of the radiomics model.Conclusions: Using pre- and posttreatment MRI data, we developed a radiomics model with excellent performance for individualized, noninvasive prediction of pCR. This model may be used to identify LARC patients who can omit surgery after chemoradiotherapy. Clin Cancer Res; 23(23); 7253-62. ©2017 AACR.

Prospective validation of pathologic complete response models in rectal cancer: Transferability and reproducibility

PURPOSE

Multiple models have been developed to predict pathologic complete response (pCR) in locally advanced rectal cancer patients. Unfortunately, validation of these models normally omit the implications of cohort differences on prediction model performance. In this work, we will perform a prospective validation of three pCR models, including information whether this validation will target transferability or reproducibility (cohort differences) of the given models.

METHODS

We applied a novel methodology, the cohort differences model, to predict whether a patient belongs to the training or to the validation cohort. If the cohort differences model performs well, it would suggest a large difference in cohort characteristics meaning we would validate the transferability of the model rather than reproducibility. We tested our method in a prospective validation of three existing models for pCR prediction in 154 patients.

RESULTS

Our results showed a large difference between training and validation cohort for one of the three tested models [Area under the Receiver Operating Curve (AUC) cohort differences model: 0.85], signaling the validation leans towards transferability. Two out of three models had a lower AUC for validation (0.66 and 0.58), one model showed a higher AUC in the validation cohort (0.70).

DISCUSSION

We have successfully applied a new methodology in the validation of three prediction models, which allows us to indicate if a validation targeted transferability (large differences between training/validation cohort) or reproducibility (small cohort differences).

Sequential PET/CT with [18F]-FDG Predicts Pathological Tumor Response to Preoperative Short Course Radiotherapy with Delayed Surgery in Patients with Locally Advanced Rectal Cancer Using Logistic Regression Analysis

Previous studies indicate that FDG PET/CT may predict pathological response in patients undergoing neoadjuvant chemo-radiotherapy for locally advanced rectal cancer (LARC). Aim of the current study is evaluate if pathological response can be similarly predicted in LARC patients after short course radiation therapy alone. Methods: Thirty-three patients with cT2-3, N0-2, M0 rectal adenocarcinoma treated with hypo fractionated short course neoadjuvant RT (5x5 Gy) with delayed surgery (SCRTDS) were prospectively studied. All patients underwent 3 PET/CT studies at baseline, 10 days from RT end (early), and 53 days from RT end (delayed). Maximal standardized uptake value (SUVmax), mean standardized uptake value (SUVmean) and total lesion glycolysis (TLG) of the primary tumor were measured and recorded at each PET/CT study. We use logistic regression analysis to aggregate different measures of metabolic response to predict the pathological response in the course of SCRTDS. Results: We provide straightforward formulas to classify response and estimate the probability of being a major responder (TRG1-2) or a complete responder (TRG1) for each individual. The formulas are based on the level of TLG at the early PET and on the overall proportional reduction of TLG between baseline and delayed PET studies. Conclusions: This study demonstrates that in the course of SCRTDS it is possible to estimate the probabilities of pathological tumor responses on the basis of PET/CT with FDG. Our formulas make it possible to assess the risks associated to LARC borne by a patient in the course of SCRTDS. These risk assessments can be balanced against other health risks associated with further treatments and can therefore be used to make informed therapy adjustments during SCRTDS.

Rectal Cancer: Assessment of Neoadjuvant Chemoradiation Outcome based on Radiomics of Multiparametric MRI

PURPOSE

To evaluate multiparametric MRI features in predicting pathologic response after preoperative chemoradiation therapy (CRT) for locally advanced rectal cancer (LARC).

EXPERIMENTAL DESIGN

Forty-eight consecutive patients (January 2012-November 2014) receiving neoadjuvant CRT were enrolled. All underwent anatomical T1/T2, diffusion-weighted MRI (DWI) and dynamic contrast-enhanced (DCE) MRI before CRT. A total of 103 imaging features, analyzed using both volume-averaged and voxelized methods, were extracted for each patient. Univariate analyses were performed to evaluate the capability of each individual parameter in predicting pathologic complete response (pCR) or good response (GR) evaluated based on tumor regression grade. Artificial neural network with 4-fold validation technique was further utilized to select the best predictor sets to classify different response groups and the predictive performance was calculated using receiver operating characteristic (ROC) curves.

RESULTS

The conventional volume-averaged analysis could provide an area under ROC curve (AUC) ranging from 0.54 to 0.73 in predicting pCR. While if the models were replaced by voxelized heterogeneity analysis, the prediction accuracy measured by AUC could be improved to 0.71-0.79. Similar results were found for GR prediction. In addition, each subcategory images could generate moderate power in predicting the response, which if combining all information together, the AUC could be further improved to 0.84 for pCR and 0.89 for GR prediction, respectively.

CONCLUSIONS

Through a systematic analysis of multiparametric MR imaging features, we are able to build models with improved predictive value over conventional imaging metrics. The results are encouraging, suggesting the wealth of imaging radiomics should be further explored to help tailoring the treatment into the era of personalized medicine. Clin Cancer Res; 22(21); 5256-64. ©2016 AACR.

Clinical practice guidelines for the surgical treatment of rectal cancer: a consensus statement of the Hellenic Society of Medical Oncologists (HeSMO)

In rectal cancer management, accurate staging by magnetic resonance imaging, neo-adjuvant treatment with the use of radiotherapy, and total mesorectal excision have resulted in remarkable improvement in the oncological outcomes. However, there is substantial discrepancy in the therapeutic approach and failure to adhere to international guidelines among different Greek-Cypriot hospitals. The present guidelines aim to aid the multidisciplinary management of rectal cancer, considering both the local special characteristics of our healthcare system and the international relevant agreements (ESMO, EURECCA). Following background discussion and online communication sessions for feedback among the members of an executive team, a consensus rectal cancer management was obtained. Statements were subjected to the Delphi methodology voting system on two rounds to achieve further consensus by invited multidisciplinary international experts on colorectal cancer. Statements were considered of high, moderate or low consensus if they were voted by ≥80%, 60-80%, or <60%, respectively; those obtaining a low consensus level after both voting rounds were rejected. One hundred and two statements were developed and voted by 100 experts. The mean rate of abstention per statement was 12.5% (range: 2-45%). In the end of the process, all statements achieved a high consensus. Guidelines and algorithms of diagnosis and treatment were proposed. The importance of centralization, care by a multidisciplinary team, adherence to guidelines, and personalization is emphasized.

PET/CT with Fluorodeoxyglucose During Neoadjuvant Chemoradiotherapy in Locally Advanced Rectal Cancer

Objective

The aim of the present study is to evaluate the accuracy of Positron Emission Tomography/Computed Tomography (PET/CT) with Fluorodeoxyglucose ([18F]FDG) to predict treatment response in patients with locally advanced rectal cancer (LARC) during neoadjuvant chemoradiotherapy.

Patients and methods

Forty-one LARC patients performed [18F]FDG-PET/CT at baseline (PET0). All patients received continuous capecitabine concomitant to radiotherapy on the pelvis, followed by intermittent capecitabine until two weeks before curative surgery. [18F]FDG-PET/CT was also carried out at 40 Gy-time (PET1) and at the end of neoadjuvant therapy (PET2). PET imaging was analysed semi-quantitatively through the measurement of maximal standardised uptake value (SUVmax) and the tumour volume (TV). Histology was expressed through pTNM and Dworak tumor regression grading. Patients were categorised into responder (downstaging or downsizing) and non-responder (stable or progressive disease by comparison pretreatment parameters with clinical/pathological characteristics posttreatment/after surgery).

Logistic regression was used to evaluate SUVmax and TV absolute and percent reduction as predictors of response rate using gender, age, and CEA as covariates. Progression-free survival (PFS) and overall survival (OS) were estimated by the Kaplan-Meier method. Survivals were compared by the Log-Rank test.

Results

Twenty-three responders (9 ypCR, 14 with downstaged disease) and 18 non-responders showed differences in terms of both early and posttreatment SUVmax percent reduction (median comparison: responder = 63.2%, non-responder = 44.2%, p = 0.04 and responder = 76.9%, non-responder = 61.6%, p = 0.06 respectively). The best predictive cut-offs of treatment response for early and posttreatment SUVmax percent reduction were ≥57% and ≥66% from baseline (p = 0.02 and p = 0.01 respectively).

Conclusions

[18F]FDG-PET/CT is a reliable technique for evaluating therapy response during neoadjuvant treatment in LARC, through a categorical classification of the SUV max reduction during treatment.

Combined value of apparent diffusion coefficient-standardized uptake value max in evaluation of post-treated locally advanced rectal cancer

AIM: To assess the clinical diagnostic value of functional imaging, combining quantitative parameters of apparent diffusion coefficient (ADC) and standardized uptake value (SUV)max, before and after chemo-radiation therapy, in prediction of tumor response of patients with rectal cancer, related to tumor regression grade at histology.

METHODS: A total of 31 patients with biopsy proven diagnosis of rectal carcinoma were enrolled in our study. All patients underwent a whole body ¹⁸FDG positron emission tomography (PET)/computed tomography (CT) scan and a pelvic magnetic resonance (MR) examination including diffusion weighted (DW) imaging for staging (PET1, RM1) and after completion (6.6 wk) of neoadjuvant treatment (PET2, RM2). Subsequently all patients underwent total mesorectal excision and the histological results were compared with imaging findings. The MR scanning, performed on 1.5 T magnet (Philips, Achieva), included T2-weighted multiplanar imaging and in addition DW images with b-value of 0 and 1000 mm²/s. On PET/CT the SUVmax of the rectal lesion were calculated in PET1 and PET2. The percentage decrease of SUVmax (ΔSUV) and ADC (ΔADC) values from baseline to presurgical scan were assessed and correlated with pathologic response classified as tumor regression grade (Mandard’s criteria; TRG1 = complete regression, TRG5 = no regression).

RESULTS: After completion of therapy, all the patients were submitted to surgery. According to the Mandard’s criteria, 22 tumors showed complete (TRG1) or subtotal regression (TRG2) and were classified as responders; 9 tumors were classified as non responders (TRG3, 4 and 5). Considering all patients the mean values of SUVmax in PET 1 was higher than the mean value of SUVmax in PET 2 (P < 0.001), whereas the mean ADC values was lower in RM1 than RM2 (P < 0.001), with a ΔSUV and ΔADC respectively of 60.2% and 66.8%. The best predictors for TRG response were SUV2 (threshold of 4.4) and ADC2 (1.29 × 10^-3 mm²/s) with high sensitivity and specificity. Combining in a single analysis both the obtained median value, the positive predictive value, in predicting the different group category response in related to TRG system, presented R² of 0.95.

CONCLUSION: The functional imaging combining ADC and SUVmax in a single analysis permits to detect changes in cellular tissue structures useful for the assessment of tumour response after the neoadjuvant therapy in rectal cancer, increasing the sensitivity in correct depiction of treatment response than either method alone.

New Perspectives on Predictive Biomarkers of Tumor Response and Their Clinical Application in Preoperative Chemoradiation Therapy for Rectal Cancer

Preoperative chemoradiation therapy (CRT) is the standard treatment for patients with locally advanced rectal cancer (LARC) and can improve local control and survival outcomes. However, the responses of individual tumors to CRT are not uniform and vary widely, from complete response to disease progression. Patients with resistant tumors can be exposed to irradiation and chemotherapy that are both expensive and at times toxic without benefit. In contrast, about 60% of tumors show tumor regression and T and N down-staging. Furthermore, a pathologic complete response (pCR), which is characterized by sterilization of all tumor cells, leads to an excellent prognosis and is observed in approximately 10-30% of cases. This variety in tumor response has lead to an increased need to develop a model predictive of responses to CRT in order to identify patients who will benefit from this multimodal treatment. Endoscopy, magnetic resonance imaging, positron emission tomography, serum carcinoembryonic antigen, and molecular biomarkers analyzed using immunohistochemistry and gene expression profiling are the most commonly used predictive models in preoperative CRT. Such modalities guide clinicians in choosing the best possible treatment options and the extent of surgery for each individual patient. However, there are still controversies regarding study outcomes, and a nomogram of combined models of future trends is needed to better predict patient response. The aim of this article was to review currently available tools for predicting tumor response after preoperative CRT in rectal cancer and to explore their applicability in clinical practice for tailored treatment.

[Preoperative chemoradiotherapy for rectal cancer: experience from one centre]

PURPOSE

In recent decades, the management of rectal cancer has been significantly improved by optimizing the surgical treatment with the total mesorectal excision and the development of neoadjuvant radiotherapy with or without chemotherapy. In this study, we investigated the impact of changes in practice over a period of 15 years in an expert centre.

PATIENTS AND METHODS

A monocentric study was conducted retrospectively on cT3-resectable T4 patients who received chemoradiotherapy for a locally advanced rectal adenocarcinoma between 1993 and 2008. We studied sphincter preservation, pathological complete response (ypT0), survival, and toxicities by different concomitant chemotherapy and treatment period.

RESULTS

Among the 179 patients who had a chemoradiotherapy, 56.4% were received concomitant 5-fluoro-uracil-leucovorin, 28.5% with concomitant capecitabine, and 15.1% with concomitant oxaliplatin and capecitabine. The average dose of radiotherapy was 45 Gy (25×1.8 Gy). Five-year disease-free survival was 74.3% and overall survival 68.8%. The rate of local recurrence and distant metastases were 6.1 and 23.6%. In multivariate analysis, concomitant chemotherapy oxaliplatin and capecitabine improved the pathological complete response rate (ypT0; capecitabine: 6%, 5-fluoro-uracil-leucovorin: 10.3%, capecitabine-oxaliplatin: 22.2%), but not significantly (P=0.12) and with more toxicities, and treatment interruptions. Sphincter preservation rate was not improved significantly during the study period (1993-2004 vs. 2005-2008), but disease-free survival improved from 72.2% up to 87.5% (P=0.03).

CONCLUSION

Our results are consistent with those published in the literature. Concomitant chemotherapy with 5-fluoro-uracil or capecitabine remains the standard scheme. Upfront chemotherapy, before chemoradiotherapy, should be investigated with regard to the predominance of metastasis.

Computerized PET/CT image analysis in the evaluation of tumour response to therapy

Current cancer therapy strategy is mostly population based, however, there are large differences in tumour response among patients. It is therefore important for treating physicians to know individual tumour response. In recent years, many studies proposed the use of computerized positron emission tomography/CT image analysis in the evaluation of tumour response. Results showed that computerized analysis overcame some major limitations of current qualitative and semiquantitative analysis and led to improved accuracy. In this review, we summarize these studies in four steps of the analysis: image registration, tumour segmentation, image feature extraction and response evaluation. Future works are proposed and challenges described.

The predictive value of 18F-FDG PET/CT for assessing pathological response and survival in locally advanced rectal cancer after neoadjuvant radiochemotherapy

PURPOSE

To evaluate whether metabolic changes in the primary tumour during and after preoperative radiochemotherapy (RCT) can predict the histopathological response in patients with locally advanced rectal cancer as well as disease-free survival (DFS) and overall survival (OS).

METHODS

Consecutive patients with cT2-4 N0-2 rectal adenocarcinoma were included. (18)F-FDG PET/CT was performed at baseline, at the end of the second week of RCT (early PET/CT) and before surgery (late PET/CT). The PET/CT results were compared with histopathological data (ypT0 N0 vs. ypT1-4 N0-2 as well as TRG1 vs.TRG2-5) and survival.

RESULTS

The study included 126 patients. Among 124 patients in whom TNM classification was available, 28 (22.6 %) were ypT0 N0, and among all 126 patients, 31 (24.6 %) were TRG1. The areas under the curve of the early response index (RI) for identifying non-complete pathological response (non-cPR) were 0.74 (95 % CI 0.61 - 0.87) for ypT1-4 N0-2 patients and 0.75 (95 % CI 0.62 - 0.88) for TRG2-5 patients. The optimal cut-off for differentiating patients with non-cPR and cPR was found to be a reduction of 61.2 % (83.1 % sensitivity and 65 % specificity in ypT1-4 N0-2 patients; 85.4 % sensitivity and 65.2 % specificity in TRG2-5 patients). The optimal cut-off for late RI could not be found. The qualitative analysis of images obtained after RCT demonstrated 81.5 % sensitivity and 61.3 % specificity in predicting TRG2-5. After a median follow-up of 68 months, the low number of patients with local/distant recurrence or who had died did not allow the value of PET/CT for predicting DFS and OS to be calculated.

CONCLUSION

The early assessment of response to RCT by (18)F-FDG PET/CT can predict non-cPR allowing practical modification of preoperative treatment. Conversely, late RI is not sufficiently accurate for guiding the decision as to whether local excision or even observation is appropriate in an individual patient. Qualitative analysis of late PET/CT images is also not sensitive enough alone to rule out the presence of residual disease.

Gradient-based delineation of the primary GTV on FLT PET in squamous cell cancer of the thoracic esophagus and impact on radiotherapy planning

Background

To validate a gradient-based segmentation method for gross tumor volume(GTV) delineation on ⁸F-fluorothymidine (FLT)positron emission tomography (PET)/ computer tomography (CT) in esophageal squamous cell cancer through pathologic specimen, in comparison with standardized uptake values (SUV) threshold-based methods and CT. The corresponding impact of this GTV delineation method on treatment planning was evaluated.

Methods and materials

Ten patients with esophageal squamous cell cancer were enrolled. Before radical surgery, all patients underwent FLT-PET/CT. GTVs were delineated by using four methods. GTV_GRAD, GTV_1.4 and GTV_30%max were segmented on FLT PET using a gradient-based method, a fixed threshold of 1.4 SUV and 30% of SUV_max, respectively. GTV_CT was based on CT data alone. The maximum longitudinal tumor length of each segmented GTV was compared with the measured tumor length of the pathologic gross tumor length (L_Path). GTV_GRAD, GTV_1.4 and GTV_30%max were compared with GTV_CT by overlap index. Two radiotherapy plannings (plan_GRAD) and (plan_CT) were designed for each patient based on GTV_GRAD and GTV_CT. The dose-volume parameters for target volume and normal tissues, CI and HI of plan_GRAD and plan_CT were compared.

Results

The mean ± standard deviation of L_Path was 6.47 ± 2.70 cm. The mean ± standard deviation of L_GRAD,L_1.4, L_30%max and L_CT were 6.22 ± 2.61, 6.23 ± 2.80, 5.95 ± 2.50,7.17 ± 2.28 cm, respectively. The Pearson correlation coefficients between L_Path and each segmentation method were 0.989, 0.920, 0.920 and 0.862, respectively. The overlap indices of GTV_GRAD, GTV_1.4, GTV_30%max when compared with GTV_CT were 0.75 ± 0.12, 0.71 ± 0.12, 0.57 ± 0.10, respectively. The V₅, V₁₀, V₂₀, V₃₀ and mean dose of total-lung,V₃₀ and mean dose of heart of plan_GRAD were significantly lower than plan_CT.

Conclusions

The gradient-based method provided the closest estimation of target length. The radiotherapy plannings based on the gradient-based segmentation method reduced the irradiated volume of lung, heart in comparison to CT.

Dynamic contrast enhanced MR imaging for rectal cancer response assessment after neo-adjuvant chemoradiation

BACKGROUND

Patient selection for organ sparing treatment after good response to neo-adjuvant chemoradiation (CRT) for locally advanced rectal cancer is challenging as no optimal restaging modality is available after CRT. In this study, we assessed the value of dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) for rectal cancer pathological response prediction.

METHODS

In 51 patients with locally advanced rectal cancer, the tumor volume and volume transfer constant (Ktrans) were obtained at 3 Tesla before CRT and surgery. The predictive potential for pathological complete response (pCR) and good response (GR) was assessed. GR was defined as pCR and near-pCR based on the tumor regression grade.

RESULTS

The GR group consisted of 10 patients (19.6%) with six pCR (11.8%). Both the post-CRT tumor volume and post-CRT Ktrans values and the relative change in volume (ΔVolume) and Ktrans (ΔKtrans) were predictive for pathological response. ΔKtrans showed the best predictive potential with a positive predictive value (PPV) of 100% for GR using a cutoff value of 32% reduction in Ktrans. For pCR the best PPV was 80% with a multiparameter model containing ΔVolume and ΔKtrans.

CONCLUSION

DCE-MRI has predictive potential for pathological response after CRT in rectal cancer with the relative ΔKtrans being the most predictive parameter.

Tumor SUVmax Normalized to Liver Uptake on (18)F-FDG PET/CT Predicts the Pathologic Complete Response After Neoadjuvant Chemoradiotherapy in Locally Advanced Rectal Cancer

PURPOSE

This study investigates the feasibility of using (18)F-fluorodeoxyglucose positron emission tomography/computed tomography ((18)F-FDG PET/CT) to predict the pCR (pathologic complete response) rate after neoadjuvant chemoradiotherapy (NCRT) in patients with locally advanced rectal cancer.

METHODS

A total of 88 patients with locally advanced rectal cancer were retrospectively analyzed. All patients were treated with NCRT, followed by radical surgery, and (18)F-FDG PET/CT was performed before and after NCRT. For a semiquantitative assessment, a volume of interest was drawn, including the whole tumor region, and the maximum SUV (SUVmax), SUVmax normalized to liver uptake (SLR), SUVmax normalized to blood pool uptake (SBR), the metabolic tumor volume at SUV 2.0 (MTV[2.0]), SUV 2.5 (MTV[2.5]), and SUV 3.0 (MTV[3.0]) were measured. In addition, their percentage changes after NCRT were assessed. The pCR was verified through a histologic examination of postsurgical specimens. A receiver operating characteristic curve analysis was conducted to predict the pCR by using these PET parameters.

RESULTS

The pCR was predicted in 17 patients (19 %). The values of the area under the curve (AUC) for predicting the pCR were 0.774 for SUVmax after NCRT, 0.826 for SLR after NCRT, 0.815 for SBR after NCRT, 0.724 for MTV(2.5) after NCRT, 0.729 for the percentage change in SUVmax, 0.700 for the percentage change in SLR, and 0.749 for the percentage change in MTV (2.5). Among these PET parameters, SLR after NCRT showed the highest AUC value. The optimal criterion, sensitivity, specificity, and accuracy of SLR after NCRT for predicting the pCR were ≤1.41, 88 %, 65 %, and 68 %, respectively.

CONCLUSIONS

F-FDG PET was found to be useful for predicting the pCR after NCRT in patients with locally advanced rectal cancer. Among various PET parameters, SUVmax normalized to liver uptake after NCRT was the best predictor of the pCR.

Functional imaging of the bowel

Functional imaging techniques enable physiological information to be derived, which, combined with high-resolution anatomical imaging, has the potential to improve the management of patients with intestinal disease. Two of the common pathologies where imaging has a substantial role in depicting disease extent, in staging disease, and assessing therapeutic response and/or disease relapse are cancer and inflammatory bowel disease. In these scenarios, functional imaging may augment assessment of disease activity, therapeutic response/non-response, as well as disease relapse by indicating physiological changes as a result of tumor, inflammation, or fibrosis.

Value of gadofosveset-enhanced MRI and multiplanar reformatting for selecting good responders after chemoradiation for rectal cancer

OBJECTIVES

Our primary objective was to evaluate diagnostic performance of gadofosveset T1-weighted magnetic resonance imaging (T1W MRI) for discriminating between ypT0-2 and ypT3-4 tumours after chemoradiation therapy (CRT) for rectal cancer compared with T2W MRI for a general and expert reader. Second objectives included assessing the value of multiplanar reformatting (MPR) and interobserver agreement.

METHODS

A general and expert reader evaluated 49 patients for likelihood of ypT0-2 tumour after CRT on T2W, gadofosveset T1W MRI, and gadofosveset T1W MRI + T2W MRI. The general reader scored with and without MPR. Confidence level scores were used to construct receiver-operating characteristic (ROC) curves. Area under the curve (AUC) values and diagnostic parameters were calculated and compared.

RESULTS

Gadofosveset T1W MRI + T2W MRI showed slightly superior sensitivity than T2W MRI for the general but not the expert reader. Specificity was higher for the expert on gadofosveset T1W MRI only compared with T2W MRI only (100% vs. 82%). MPR did not increase diagnostic performance. Interobserver agreement was highest for the combination of gadofosveset-enhanced T1W imaging plus T2W MRI.

CONCLUSIONS

The sole use or addition of gadofosveset-enhanced T1W MRI to T2W MRI did not increase significantly diagnostic performance for assessing ypT0-2 tumours. Adding gadofosveset-enhanced T1W MRI slightly increased sensitivity for the general reader and specificity for the expert reader, but this increase was not significant for more accurate clinical decision making. MPR did not improve diagnostic performance.

KEY POINTS

• ycT restaging with MRI in rectal cancer is challenging. • Gadofosveset-enhanced T1W MRI has shown promise for nodal restaging. • Gadofosveset-enhanced T1W MRI did not significantly increase diagnostic performance for assessing ypT0-2-tumours. • Addition of the gadofosveset sequence to T2W MRI slightly increased sensitivity for the general reader. • MPR did not improve diagnostic performance of ycT staging.

Voxel-based dual-time 18F-FDG parametric imaging for rectal cancer: differentiation of residual tumor from postchemoradiotherapy changes

Supplemental Digital Content is available in the text.

Introduction

¹⁸F-Fluorodeoxyglucose (¹⁸F-FDG) PET/computed tomography (CT) has been used for evaluation of the response of rectal cancer to neoadjuvant chemoradiotherapy (CRT), but differentiating residual tumor from post-treatment changes remains a problem. We propose a voxel-based dual-time ¹⁸F-FDG PET parametric imaging technique for the evaluation of residual rectal cancer after CRT.

Materials and methods

Eighty-six patients with locally advanced rectal cancer who underwent neoadjuvant CRT between March 2009 and February 2011 were selected retrospectively. Standard 60-min postinjection PET/CT scans followed by 90-min delayed images were coregistered by rigid-body transformation. A dual-time parametric image was generated, which divided delayed standardized uptake value (SUV) by 60-min SUV on a voxel-by-voxel basis. Maximum delayed-to-standard SUV ratios (DSR) measured on the parametric images as well as the percentage of SUV decrease from pre-CRT to post-CRT scans (pre/post-CRT response index) were obtained for each tumor and correlated with pathologic response classified by the Dworak tumor regression grade (TRG).

Results

With respect to the false-positive lesions in the nine post-CRT patients with false-positive standard ¹⁸F-FDG scans in case groups who responded to therapy (TRG 3 or 4 tumors), eight were undetectable on dual-time parametric images (P<0.05). The maximum DSR showed significantly higher accuracy for identification of tumor regression compared with the pre/post-CRT response index in receiver-operating characteristic analysis (P<0.01). With a 1.25 cutoff value for the maximum DSR, 85.0% sensitivity, 95.5% specificity, and 93.0% overall accuracy were obtained for identification of good response.

Conclusion

A voxel-based dual-time parametric imaging technique for evaluation of post-CRT rectal cancer holds promise for differentiating residual tumor from treatment-related nonspecific ¹⁸F-FDG uptake.

Predicting pathologic tumor response to chemoradiotherapy with histogram distances characterizing longitudinal changes in 18F-FDG uptake patterns

PURPOSE

A family of fluorine-18 ((18)F)-fluorodeoxyglucose ((18)F-FDG) positron-emission tomography (PET) features based on histogram distances is proposed for predicting pathologic tumor response to neoadjuvant chemoradiotherapy (CRT). These features describe the longitudinal change of FDG uptake distribution within a tumor.

METHODS

Twenty patients with esophageal cancer treated with CRT plus surgery were included in this study. All patients underwent PET/CT scans before (pre-) and after (post-) CRT. The two scans were first rigidly registered, and the original tumor sites were then manually delineated on the pre-PET/CT by an experienced nuclear medicine physician. Two histograms representing the FDG uptake distribution were extracted from the pre- and the registered post-PET images, respectively, both within the delineated tumor. Distances between the two histograms quantify longitudinal changes in FDG uptake distribution resulting from CRT, and thus are potential predictors of tumor response. A total of 19 histogram distances were examined and compared to both traditional PET response measures and Haralick texture features. Receiver operating characteristic analyses and Mann-Whitney U test were performed to assess their predictive ability.

RESULTS

Among all tested histogram distances, seven bin-to-bin and seven crossbin distances outperformed traditional PET response measures using maximum standardized uptake value (AUC = 0.70) or total lesion glycolysis (AUC = 0.80). The seven bin-to-bin distances were: L(2) distance (AUC = 0.84), χ(2) distance (AUC = 0.83), intersection distance (AUC = 0.82), cosine distance (AUC = 0.83), squared Euclidean distance (AUC = 0.83), L(1) distance (AUC = 0.82), and Jeffrey distance (AUC = 0.82). The seven crossbin distances were: quadratic-chi distance (AUC = 0.89), earth mover distance (AUC = 0.86), fast earth mover distance (AUC = 0.86), diffusion distance (AUC = 0.88), Kolmogorov-Smirnov distance (AUC = 0.88), quadratic form distance (AUC = 0.87), and match distance (AUC = 0.84). These crossbin histogram distance features showed slightly higher prediction accuracy than texture features on post-PET images.

CONCLUSIONS

The results suggest that longitudinal patterns in (18)F-FDG uptake characterized using histogram distances provide useful information for predicting the pathologic response of esophageal cancer to CRT.

18F-FDG PET predicts pathological response to preoperative chemoradiotherapy in patients with primary rectal cancer: a meta-analysis

OBJECTIVE

The aim of this study was to assess the performance of fluorine-18-fluorodeoxyglucose (18F-FDG) positron emission tomography (PET) in predicting pathological response to preoperative chemoradiotherapy (CRT) in patients with primary rectal cancer.

METHODS

Potentially relevant articles were searched in the databases of PubMed and Embase from January 1990 to September 2013. The Quality Assessment for Diagnostic Accuracy Studies criteria was employed to assess the quality of all of the included studies. The pooled sensitivity and specificity were calculated, and the area under the curve of the summary receiver operating characteristic curve was obtained. Subgroup analysis was conducted to explore the sources of heterogeneity.

RESULTS

Thirty-one eligible studies involving 1527 patients were ultimately included in the meta-analysis. Four main quantitative or qualitative parameters [response index (RI), post-treatment maximum standardized uptake value (SUVmax-post), visual response (VR) and the percentage change in total lesion glycolysis (TLG) before and after CRT (deltaTLG%)] related to PET or positron emission tomography/computed tomography (PET/CT) were assessed for the prediction of histopathological response. The pooled sensitivities of these four parameters were comparable and were 74, 74, 75 and 78%, respectively (P>0.05). The pooled specificity of deltaTLG% was higher than that of the other three parameters (RI, SUVmax-post and VR) and was 81, 66, 64 and 67%, respectively (P<0.05). The results from subgroup analysis showed that the RI and SUVmax-post had higher specificity in predicting tumor regression grade (TRG) than complete pathological response (pCR) [RI, 71 vs. 59% (P=0.0275); SUVmax-post, 72 vs. 61% (P=0.0178)].The diagnostic sensitivity and specificity of the RI and SUVmax-post when the post-treatment PET or PET/CT scan was performed at two different time points (during CRT and after the completion of CRT) were 82 vs. 72% (P=0.0630) and 78 vs. 63% (P=0.0059), respectively.

CONCLUSIONS

18F-FDG PET could be a potentially powerful non-invasive tool for predicting pathological response; the related parameters RI and SUVmax-post may be more suitable for the prediction of TRG than pCR. The current data also suggested that the optimum post-treatment 18F-FDG PET scan could be carried out during CRT.

International data-sharing for radiotherapy research: an open-source based infrastructure for multicentric clinical data mining

Extensive, multifactorial data sharing is a crucial prerequisite for current and future (radiotherapy) research. However, the cost, time and effort to achieve this are often a roadblock. We present an open-source based data-sharing infrastructure between two radiotherapy departments, allowing seamless exchange of de-identified, automatically translated clinical and biomedical treatment data.

Neither FDG-PET Nor CT can distinguish between a pathological complete response and an incomplete response after neoadjuvant chemoradiation in locally advanced rectal cancer: a prospective study

OBJECTIVE

To prospectively compare the ability of flourodeoxyglucose-positron emission tomography (FDG-PET) and computed tomography (CT) to identify a pathological complete response (pCR) in patients with rectal cancer treated by chemoradiation.

BACKGROUND

A major obstacle in pursuing nonoperative management in patients with rectal cancer after chemoradiation is the inability to identify a pCR preoperatively.

METHODS

A total of 121 patients with rectal cancer were prospectively enrolled. FDG-PET scans and helical CT scans were obtained before and after neoadjuvant chemoradiation. Consensus readings of PET and CT scans were used to classify certainty of disease (5-point confidence rating scale). The ability of PET and CT scans to accurately distinguish a pCR (ypT0) from an incomplete response (ypT1-4) was estimated using the area under the receiver operating characteristic curve (AUC).

RESULTS

Of the 121 patients, 26 (21%) had a pCR. PET and CT scans were equally inadequate at distinguishing a pCR from an incomplete response (AUC = 0.64 for both, P = 0.97). Among the 26 patients with a pCR, 14 (54%) and 5 (19%) were classified as complete responders on PET and CT scans, respectively. Among the 95 patients with an incomplete pathological response, 63 (66%) and 90 (95%) were classified as incomplete responders on PET and CT scans, respectively. None of the individual PET parameters, including visual response score, mean standard uptake value (SUVmean), maximum SUV (SUVmax), and total lesion glycolysis, accurately distinguished a pCR (AUCs = 0.57-0.73).

CONCLUSIONS

Neither PET nor CT scans have adequate predictive value to be clinically useful in distinguishing a pCR from an incomplete response and, therefore, should not be obtained for the purpose of attempting to predict a pCR after neoadjuvant chemoradiation for rectal cancer.

New application of dual point 18F-FDG PET/CT in the evaluation of neoadjuvant chemoradiation response of locally advanced rectal cancer

PURPOSE

FDG PET/CT has been suggested as the most reliable modality to predict pathological tumor responses after neoadjuvant chemoradiotherapy (CRT) in locally advanced rectal cancer (LARC). However, several confounding factors including radiation-induced inflammation could not be easily avoided with the commonly used single-point FDG PET/CT. Our aim was to evaluate the accuracy of a dual-point PET/CT protocol in LARC response prediction to CRT.

PATIENTS AND METHODS

Sixty-one LARC patients were enrolled and treated with neoadjuvant CRT. PET/CT was performed before and after CRT. Dual-point acquisition was applied to post-CRT PET/CT. Post-CRT SUVmax (postSUV), pre/post-CRT SUVmax change (RI), and dual-point index (DI) of post-CRT PET/CT were compared with the Dworak tumor regression grade (TRG) as a gold standard. Univariate and multivariate analyses, as well as receiver operating characteristic curve analysis, were used to evaluate the predictive ability of demographic, clinical, and metabolic PET parameters.

RESULTS

Fifteen patients of TRG3-4 were defined as pathological responders, and 46 patients of TRG1-2 were nonresponders. The resulting response index (RI) ranged from -13 to 94.8% (59.1±22.0%), and delay index (DI) ranged from -45.2 to 25.0% (-9.1±12.1%). Univariate analysis resulted in PET parameters (postSUV, RI, and DI) as significant predictors (P=0.004, P<0.001, P<0.0001). According to multivariate analysis, RI and DI remained as significant predictors (P=0.04 and P=0.0004). Receiver operating characteristic analysis showed that DI had significantly higher area under the curve compared with RI (0.906 vs 0.696, P=0.018). Delay index had 86.7% sensitivity, 87.0% specificity, 68.4% positive predictive value, 95.2% negative predictive value, and 86.9% accuracy.

CONCLUSIONS

Dual-point post-CRT PET/CT can predict pathological tumor response better than conventional single time point pre- and post-CRT PET/CT.

Early prediction of pathological response in locally advanced rectal cancer based on sequential 18F-FDG PET

BACKGROUND

The objectives of this study were to investigate the predictive value of sequential (18)F-FDG PET scans for pathological tumor response grade (TRG) after preoperative chemoradiotherapy (PCRT) in locally advanced rectal cancer (LARC) and the impact of partial volume effects correction (PVC).

METHODS

Twenty-eight LARC patients were included. Responders and non-responders status were determined in histopathology. PET indices [SUV max and mean, volume and total lesion glycolysis (TLG)] at baseline and their evolution after one and two weeks of PCRT were extracted by delineation of the PET images, with or without PVC. Their predictive value was investigated using Mann-Whitney-U tests and ROC analysis.

RESULTS

Within baseline parameters, only SUVmean was correlated with response. No evolution after one week was predictive of the response, whereas after two weeks all the parameters except volume were, the best prediction being obtained with TLG (AUC 0.79, sensitivity 63%, specificity 92%). PVC had no significant impact on these results.

CONCLUSION

Several PET indices at baseline and their evolution after two weeks of PCRT are good predictors of response in LARC, with or without PVC, whereas results after one week are suboptimal. Best predictor was TLG reduction after two weeks, although baseline SUVmean had smaller but similar predictive power.

Early FDG PET response assessment of preoperative radiochemotherapy in locally advanced rectal cancer: correlation with long-term outcome

PURPOSE

The aim of the present study is to prospectively evaluate the prognostic value of previously defined [(18)F]2-fluoro-2-deoxy-D-glucose positron emission tomography (FDG PET) criteria of early metabolic response in patients with locally advanced rectal cancer (LARC) after long-term follow-up.

METHODS

Forty-two patients with poor prognosis LARC underwent three biweekly courses of chemotherapy with oxaliplatin, raltitrexed and 5-fluorouracil modulated by levofolinic acid during pelvic radiotherapy. FDG PET studies were performed before and 12 days after the beginning of the chemoradiotherapy (CRT) treatment. Total mesorectal excision (TME) was carried out 8 weeks after completion of CRT. A previously identified cutoff value of ≥52 % reduction of the baseline mean FDG standardized uptake value (SUV(mean)) was applied to differentiate metabolic responders from non-responders and correlated to tumour regression grade (TRG) and survival.

RESULTS

Twenty-two metabolic responders showed complete (TRG1) or subtotal tumour regression (TRG2) and demonstrated a statistically significantly higher 5-year relapse-free survival (RFS) compared with the 20 non-responders (86 vs 55 %, p = .014) who showed TRG3 and TRG4 pathologic responses. A multivariate analysis demonstrated that early ∆SUV(mean) was the only pre-surgical parameter correlated to the likelihood of recurrence (p = .05).

CONCLUSION

This study is the first prospective long-term evaluation demonstrating that FDG PET is not only an early predictor of pathologic response but is also a valuable prognostic tool. Our results indicate the potential of FDG PET for optimizing multidisciplinary management of patients with LARC.

Early prediction of histopathological response of rectal tumors after one week of preoperative radiochemotherapy using 18 F-FDG PET-CT imaging. A prospective clinical study

BACKGROUND

Preoperative radiochemotherapy (RCT) is standard in locally advanced rectal cancer (LARC). Initial data suggest that the tumor's metabolic response, i.e. reduction of its 18 F-FDG uptake compared with the baseline, observed after two weeks of RCT, may correlate with histopathological response. This prospective study evaluated the ability of a very early metabolic response, seen after only one week of RCT, to predict the histopathological response to treatment.

METHODS

Twenty patients with LARC who received standard RCT regimen followed by radical surgery participated in this study. Maximum standardized uptake value (SUV-MAX), measured by PET-CT imaging at baseline and on day 8 of RCT, and the changes in FDG uptake (ΔSUV-MAX), were compared with the histopathological response at surgery. Response was classified by tumor regression grade (TRG) and by achievement of pathological complete response (pCR).

RESULTS

Absolute SUV-MAX values at both time points did not correlate with histopathological response. However, patients with pCR had a larger drop in SUV-MAX after one week of RCT (median: -35.31% vs -18.42%, p = 0.046). In contrast, TRG did not correlate with ΔSUV-MAX. The changes in FGD-uptake predicted accurately the achievement of pCR: only patients with a decrease of more than 32% in SUV-MAX had pCR while none of those whose tumors did not show any decrease in SUV-MAX had pCR.

CONCLUSIONS

A decrease in ΔSUV-MAX after only one week of RCT for LARC may be able to predict the achievement of pCR in the post-RCT surgical specimen. Validation in a larger independent cohort is planned.

Changes in cervical cancer FDG uptake during chemoradiation and association with response

PURPOSE

Previous research showed that pretreatment uptake of F-18 fluorodeoxyglucose (FDG), as assessed by the maximal standardized uptake value (SUVmax) and the variability of uptake (FDGhetero), predicted for posttreatment response in cervical cancer. In this pilot study, we evaluated the changes in SUVmax and FDGhetero during concurrent chemoradiation for cervical cancer and their association with post-treatment response.

METHODS AND MATERIALS

Twenty-five patients with stage Ib1-IVa cervical cancer were enrolled. SUVmax, FDGhetero, and metabolic tumor volume (MTV) were recorded from FDG-positron emission tomography (PET)/computed tomography (CT) scans performed pretreatment and during weeks 2 and 4 of treatment and were evaluated for changes and association with response assessed on 3-month post-treatment FDG-PET/CT.

RESULTS

For all patients, the average pretreatment SUVmax was 17.8, MTV was 55.4 cm3, and FDGhetero was -1.33. A similar decline in SUVmax was seen at week 2 compared with baseline and week 4 compared with week 2 (34%). The areas of highest FDG uptake in the tumor remained relatively consistent on serial scans. Mean FDGhetero decreased during treatment. For all patients, MTV decreased more from week 2 to week 4 than from pretreatment to week 2. By week 4, the average SUVmax had decreased by 57% and the MTV had decreased by 30%. Five patients showed persistent or new disease on 3-month post-treatment PET. These poor responders showed a higher average SUVmax, larger MTV, and greater heterogeneity at all 3 times. Week 4 SUVmax (P=.037), week 4 FDGhetero (P=.005), pretreatment MTV (P=.008), and pretreatment FDGhetero (P=.008) were all significantly associated with post-treatment PET response.

CONCLUSIONS

SUVmax shows a consistent rate of decline during treatment and declines at a faster rate than MTV regresses. Based on this pilot study, pretreatment and week 4 of treatment represent the best time points for prediction of response.

Long-term follow-up features on rectal MRI during a wait-and-see approach after a clinical complete response in patients with rectal cancer treated with chemoradiotherapy

BACKGROUND

The "wait-and-see" policy instead of standard surgery for patients with rectal cancer who undergo a complete tumor regression after chemoradiation treatment is highly controversial. It is not clear yet how patients should be monitored once they are managed nonoperatively and whether follow-up by MRI has any potential role.

OBJECTIVE

This study aimed to describe the rectal wall MRI morphology during short-term and long-term follow-up in patients with a clinical complete tumor response undergoing a wait-and-see policy without surgical treatment.

DESIGN, SETTING, AND PATIENTS

As part of an observational study in our center, a cohort of 19 carefully selected patients with a clinical complete response after chemoradiation was managed with a wait-and-see policy and followed regularly (every 3-6 mo) by clinical examination, endoscopy with biopsies, and a rectal MRI. The MR morphology of the tumor bed was studied on the consecutive MRI examinations.

MAIN OUTCOME MEASURES

The primary outcome measured was the morphology of the tumor bed on the consecutive MRI examinations performed during short-term (≤6 mo) and long-term (>6 mo) follow-up.

RESULTS

Patients with a complete tumor response after chemoradiation presented with either a normalized rectal wall (26%) or fibrosis (74%). In the latter group, 3 patterns of fibrosis were observed (full-thickness, minimal, or spicular fibrosis). The morphology patterns of a normalized rectal wall or fibrosis remained consistent during long-term follow-up in 18 of 19 patients. One patient developed a small, endoluminal recurrence, which was salvaged with transanal endoscopic microsurgery. In 26% of patients, an edematous wall thickening was observed in the first months after chemoradiation, which gradually decreased during long-term follow-up. Median follow-up was 22 months (range, 12-60).

LIMITATIONS

This was a small observational study, and had no histological validation.

CONCLUSIONS

Four MR patterns of a persistent complete response of rectal cancer after chemoradiation were identified. These MR features can serve as a reference for the follow-up in a wait-and-see policy.

Tumor status at 12 weeks predicts survival in advanced colorectal cancer: findings from NCCTG N9741

PURPOSE

We explored the prognostic value of actual tumor measurements (TM) versus World Health Organization (WHO) criteria as three-level (responder, stable, and progression) and two-level (responder and non-responder) variables at 12 and 24 weeks as predictors of survival in Intergroup Trial N9741, a phase III trial in metastatic colorectal cancer (CRC).

METHODS

All patients with measurable disease (N = 1,188) were included. The percentage changes in TM from baseline to 12 and 24 weeks were calculated. The prognostic values of TM versus WHO criteria (as three- and two-level variables) at 12 and 24 weeks were compared, using Cox models for overall survival (OS) in a landmark analysis, adjusting for baseline tumor size, performance status, and treatment arm.

RESULTS

Tumor status at 12 weeks by WHO criteria (three or two levels) or actual TM were all strongly associated with OS. Actual TM provided no meaningful additional benefit compared with the three-level WHO criteria. Tumor status at 24 weeks was also strongly associated with survival, but added no additional prognostic value compared with the 12-week assessment. At 12 weeks, actual TM improved prognostic characterization of patients with WHO status of response, but provided no additional value in patients with stable disease or progression.

CONCLUSIONS

In N9741, the use of actual TM, or following tumor status beyond 12 weeks, did not improve survival prediction compared with a single three-level response assessment at 12 weeks, suggesting that 12-week tumor status could be an appropriate phase II trial endpoint in metastatic CRC.