Prediction of response to preoperative chemoradiotherapy in patients with locally advanced rectal cancer

Radiation-induced changes in gene expression in rectal cancer specimens

PURPOSE

The standard-of-care for locally advanced rectal cancer is radiotherapy-based neoadjuvant therapy followed by surgical resection. This article reviews the evidence of molecular changes at the transcriptome level induced through radiotherapy in rectal cancer.

METHODS

The PubMed search "(radiation OR radiotherapy) cancer (transcriptome OR "gene expression") rectal" was used. The studies taken forward utilised gene-expression data on both pre-treatment and post-treatment rectal adenocarcinoma biospecimens from patients treated with RT-based neoadjuvant strategies.

RESULTS

Twelve publications met the review criteria. There was variation in approaches in terms of design, patient population, cohort size, timing of the post-radiotherapy sampling and method of measuring gene expression. Most of the post-treatment biospecimen retrievals were at resection. The literature indicates a broad upregulation of immune activity through radiotherapy using gene-expression data.

CONCLUSION

Future studies would benefit from standardised prospective approaches to sampling to enable the inclusion of timepoints relevant to the tumour and immune response.

Baseline and early digital [ 18 F]FDG PET/CT and multiparametric MRI contain promising features to predict response to neoadjuvant therapy in locally advanced rectal cancer patients: a pilot study

OBJECTIVE

In this pilot study, we investigated the feasibility of response prediction using digital [ 18 F]FDG PET/computed tomography (CT) and multiparametric MRI before, during, and after neoadjuvant chemoradiation therapy in locally advanced rectal cancer (LARC) patients and aimed to select the most promising imaging modalities and timepoints for further investigation in a larger trial.

METHODS

Rectal cancer patients scheduled to undergo neoadjuvant chemoradiation therapy were prospectively included in this trial, and underwent multiparametric MRI and [ 18 F]FDG PET/CT before, 2 weeks into, and 6-8 weeks after chemoradiation therapy. Two groups were created based on pathological tumor regression grade, that is, good responders (TRG1-2) and poor responders (TRG3-5). Using binary logistic regression analysis with a cutoff value of P  ≤ 0.2, promising predictive features for response were selected.

RESULTS

Nineteen patients were included. Of these, 5 were good responders, and 14 were poor responders. Patient characteristics of these groups were similar at baseline. Fifty-seven features were extracted, of which 13 were found to be promising predictors of response. Baseline [T2: volume, diffusion-weighted imaging (DWI): apparent diffusion coefficient (ADC) mean, DWI: difference entropy], early response (T2: volume change, DWI: ADC mean change) and end-of-treatment presurgical evaluation MRI (T2: gray level nonuniformity, DWI: inverse difference normalized, DWI: gray level nonuniformity normalized), as well as baseline (metabolic tumor volume, total lesion glycolysis) and early response PET/CT (Δ maximum standardized uptake value, Δ peak standardized uptake value corrected for lean body mass), were promising features.

CONCLUSION

Both multiparametric MRI and [ 18 F]FDG PET/CT contain promising imaging features to predict response to neoadjuvant chemoradiotherapy in LARC patients. A future larger trial should investigate baseline, early response, and end-of-treatment presurgical evaluation MRI and baseline and early response PET/CT.

Predictive biomarkers in radioresistant rectal cancer: a systematic review

BACKGROUND AND AIMS

The treatment of locally advanced rectal cancer often consists of neoadjuvant chemoradiotherapy followed by surgery. However, approximately 15% of patients show no response to this neoadjuvant chemoradiotherapy. This systematic review aimed to identify biomarkers of innate radioresistant rectal cancer.

METHOD

Through a systematic literature search, 125 papers were included and analyzed using ROBINS-I, a Cochrane risk of bias tool for non-randomized studies of interventions. Both statistically significant and nonsignificant biomarkers were identified. Biomarkers mentioned more than once in the results or biomarkers with a low or moderate risk of bias were included as the final results.

RESULTS

Thirteen unique biomarkers, three genetic signatures, one specific pathway, and two combinations of two or four biomarkers were identified. In particular, the connection between HMGCS2, COASY, and PI3K-pathway seems promising. Future scientific research should focus on further validating these genetic resistance markers.

Whole lesion histogram analysis of apparent diffusion coefficient predicts therapy response in locally advanced rectal cancer

BACKGROUND

Whole-tumor apparent diffusion coefficient (ADC) histogram analysis is relevant to predicting the neoadjuvant chemoradiation therapy (nCRT) response in patients with locally advanced rectal cancer (LARC).

AIM

To evaluate the performance of ADC histogram-derived parameters for predicting the outcomes of patients with LARC.

METHODS

This is a single-center, retrospective study, which included 48 patients with LARC. All patients underwent a pre-treatment magnetic resonance imaging (MRI) scan for primary tumor staging and a second restaging MRI for response evaluation. The sample was distributed as follows: 18 responder patients (R) and 30 non-responders (non-R). Eight parameters derived from the whole-lesion histogram analysis (ADCmean, skewness, kurtosis, and ADC10^th, 25^th, 50^th, 75^th, 90^th percentiles), as well as the ADCmean from the hot spot region of interest (ROI), were calculated for each patient before and after treatment. Then all data were compared between R and non-R using the Mann-Whitney U test. Two measures of diagnostic accuracy were applied: the receiver operating characteristic curve and the diagnostic odds ratio (DOR). We also reported intra- and interobserver variability by calculating the intraclass correlation coefficient (ICC).

RESULTS

Post-nCRT kurtosis, as well as post-nCRT skewness, were significantly lower in R than in non-R (both P < 0.001, respectively). We also found that, after treatment, R had a larger loss of both kurtosis and skewness than non-R (∆%kurtosis and ∆skewness, P < 0.001). Other parameters that demonstrated changes between groups were post-nCRT ADC10^th, ∆%ADC10^th, ∆%ADCmean, and ROI ∆%ADCmean. However, the best diagnostic performance was achieved by ∆%kurtosis at a threshold of 11.85% (Area under the receiver operating characteristic curve [AUC] = 0.991, DOR = 376), followed by post-nCRT kurtosis = 0.78 × 10^-3 mm²/s (AUC = 0.985, DOR = 375.3), ∆skewness = 0.16 (AUC = 0.885, DOR = 192.2) and post-nCRT skewness = 1.59 × 10^-3 mm²/s (AUC = 0.815, DOR = 168.6). Finally, intraclass correlation coefficient analysis showed excellent intraobserver and interobserver agreement, ensuring the implementation of histogram analysis into routine clinical practice.

CONCLUSION

Whole-tumor ADC histogram parameters, particularly kurtosis and skewness, are relevant biomarkers for predicting the nCRT response in LARC. Both parameters appear to be more reliable than ADCmean from one-slice ROI.

A 41-Gene Pair Signature for Predicting the Pathological Response of Locally Advanced Rectal Cancer to Neoadjuvant Chemoradiation

Background and Purpose: Pathological response status is a standard reference for the early evaluation of the effect of neoadjuvant chemoradiation (nCRT) on locally advanced rectal cancer (LARC) patients. Various patients respond differently to nCRT, but identifying the pathological response of LARC to nCRT remains a challenge. Therefore, we aimed to identify a signature that can predict the response of LARC to nCRT. Material and Methods: The gene expression profiles of 111 LARC patients receiving fluorouracil-based nCRT were used to obtain gene pairs with within-sample relative expression orderings related to pathological response. These reversal gene pairs were ranked according to the mean decrease Gini index provided by the random forest algorithm to obtain the signature. This signature was verified in two public cohorts of 46 and 42 samples, and a cohort of 33 samples measured at our laboratory. In addition, the signature was used to predict disease-free survival benefits in a series of colorectal cancer datasets. Results: A 41-gene pair signature (41-GPS) was identified in the training cohort with an accuracy of 84.68% and an area under the receiver operating characteristic curve (AUC) of 0.94. In the two public test cohorts, the accuracy was 93.37 and 73.81%, with AUCs of 0.97 and 0.86, respectively. In our dataset, the AUC was 0.80. The results of the survival analysis show that 41-GPS plays an effective role in identifying patients who will respond to nCRT and have a better prognosis. Conclusion: The signature consisting of 41 gene pairs can robustly predict the clinical pathological response of LARC patients to nCRT.

Comparison of 18F-FDG PET/CT and DW-MRI in assessment of neoadjuvant radiochemotherapy response in locally advanced rectal cancer patients

OBJECTIVE

Our aim is to evaluate if different metabolic parameters obtained by ¹⁸F-FDG PET/CT and diffusion weighted magnetic resonance imaging (DW-MRI) can aid in neoadjuvant radiochemotherapy (RCT) response assessment in locally advanced rectal cancer (LARC) patients.

METHODS

Out of 20 LARC patients, who were planned to receive neoadjuvant RCT, 19 were included in this prospective study. Patients had ¹⁸F-FDG PET/CT and DW-MRI at initial staging, interim (2 weeks after onset of RCT) and after completion of RCT (post-therapy). Standardized uptake value (SUV) parameters (SUVmax, SUVmean, SUVpeak, SULpeak), metabolic tumor volume (MTV) and tumor lesion glycolysis (TLG) detected on PET images and apparent diffusion coefficient (ADC) values (for b=400 and b=1000s/mm²) obtained from DW-MRI were recorded. Postoperative tumor regression grade (TRG) was used as gold-standard, except for 2 patients who were under complete remission with non-operative management 19 months post-therapy and scored as responders.

RESULTS

On interim PET/CT, no significant difference was found among PET parameters between responders and non-responders, whereas post-therapy SUVmax, SUVpeak, MTV, SULpeak, TLG (P=0.02, P=0.014, P=0.025, P=0.007, P=0.02, respectively) and initial MTV (P=0.034) were significantly lower in responders. ADC response index (RI) was higher in responders (interim P=0.026; post-therapy: P=0.018) and ROC analysis revealed that a threshold of ADC RI>41.6% for interim MRI and >44.6% for post-therapy MRI had sensitivity and specificity of 75.0% and 90.9%, respectively.

CONCLUSIONS

While interim ¹⁸F-FDG PET/CT failed to predict therapy response during RCT, post-therapy PET could accurately differentiate responders. DW-MRI was found to be more promising in interim detection of RCT response.

Is It Time to Introduce PET/CT in Rectal Cancer Guidelines?

At the moment, international guidelines for rectal cancer suggest to consider F-FDG PET/CT scan in a few conditions: (1) at disease presentation in case of suspected or proven metastatic synchronous adenocarcinoma with potentially curable M1 disease; (2) in the recurrence workup for serial carcinoembryonic antigen level elevation; (3) in the recurrence workup with metachronous metastases documented by CT, MRI, or biopsy; (4) in case of strong contraindication to IV contrast agent administration; and (5) to evaluate an equivocal finding on a contrast-enhanced CT or MRI. PET/CT is not indicated in the follow-up or surveillance of rectal cancer. On the other hand, an attentive evaluation of the literature shows that PET/CT may also be used in some circumstances with significant levels of diagnostic accuracy. This review article aims to emphasize differences between current international guidelines and scientific literature in the role of PET/CT in rectal cancer.

Molecular Predictors of Response to Neoadjuvant Chemoradiation for Rectal Cancer

OBJECTIVES

To determine whether the expression of specific molecular markers in the rectal cancer biopsies prior to treatment, can correlate with complete tumor response to chemoradiotherapy (CRT) as determined by the pathology of the surgical specimen.

METHODS

We retrospectively examined pretreatment rectal biopsies of patients aged 18 years or older with locally advanced rectal cancer who had been treated with neoadjuvant CRT and surgical resection in our tertiary-care, university-affiliated medical center, between January 2001 and December 2011. Samples were analyzed for expression of B-cell lymphoma 2, P53, Ki67, epidermal growth factor receptor (EGFR), vascular endothelial growth factor receptor, and the tumor regression grade after CRT and radical surgery.

RESULTS

Forty-seven patients were included in the final analysis. Main outcome measures were the correlation between the expression of the molecular markers tested in the pretreatment biopsy, and complete tumor response. Complete pathologic response after CRT was attained in 27% of the patients. Percentage of cells expressing EGFR in the pretreated biopsies of patients having complete pathologic response after CRT and surgery was 33.08±7.87% compared to 19±15.36% (P=0.38), 6.66±2.83% (P<0.003), and 12.5±4.93% (P=0.033) in patients with partial response and tumor regression grades of 2, 3, and 4, respectively. The other molecular markers tested in the pretreatment biopsy did not corresponded with complete pathologic response.

CONCLUSIONS

EGFR expression pattern in the pretreatment biopsies of rectal tumors can assist in identifying patients who will benefit from neoadjuvant CRT.

Phospho-ERK levels as predictors for chemotherapy of rectal carcinoma

Treatment of rectal cancer has been vastly improved by advances in surgery and radiochemotherapy but remains an important cause of morbidity and mortality worldwide. A particular problem is the lack of predictive markers that can help to individualize treatment. The growth- and apoptosis-regulating signaling molecules ERK 1 and 2 are important to cancer growth and progression. They are activated through phosphorylation, which is initiated by a cascade involving the EGF receptor and RAS as upstream regulators. Moreover, in vitro studies indicate that phospho-ERKs interfere with 5-fluorouracil-based chemotherapy. Recently, we showed that high levels of phospho-ERKs in rectal cancer cells predict poor responses to neoadjuvant (preoperative) radiochemotherapy. We now report that preoperative phospho-ERK levels also can subdivide high-risk rectal cancer patients into a favorable and a poor prognostic group with respect to recurrence-free survival. Importantly, phospho-ERK levels were of predictive significance only in high-risk patients, who received adjuvant (postoperative) chemotherapy, but not in high-risk patients not receiving such therapy. Our results suggest that high cancer cell levels of phospho-ERK predict poor responsiveness to both preoperative and postoperative chemotherapy of rectal cancer.

Outcome and Salvage Surgery Following "Watch and Wait" for Rectal Cancer after Neoadjuvant Therapy: A Systematic Review

BACKGROUND

Currently there is no reliable test to predict pathological complete response following neoadjuvant chemoradiotherapy for rectal cancer. However, there is increasing interest in using clinical complete response as a surrogate marker, allowing a subset of patients with locally advanced rectal cancer to be allocated into a "watch and wait" pathway. Little is known about the oncological safety of the "watch and wait" approach or the rate of salvage surgery in cases of tumor regrowth. This information is critical for the implementation of this approach.

OBJECTIVE

The aim of this study is to assess the rate of salvage surgery and associated oncological outcomes for patients who develop a tumor regrowth with the "watch and wait" approach.

DATA SOURCES

Relevant studies were identified through PubMed, Embase, and Google Scholar search.

STUDY SELECTION

A systematic review was undertaken of studies assessing patients selected for the "watch and wait" approach according to PRISMA guidelines.

MAIN OUTCOME MEASURES

The associated tumor regrowth, salvage surgery, and disease-free and overall survival rates were assessed.

RESULTS

Five retrospective and 4 prospective observational studies were included into the analysis, with a total of 370 patients in the "watch and wait" group, of which 256 (69.2%) had persistent clinical complete response. Of those who had tumor regrowth, salvage surgery was possible in 83.8%. There was no difference in overall survival and disease-free survival between patients who received immediate surgery and the "watch and wait" group.

LIMITATIONS

The limitations of this study include its retrospective nature and small sample size. Furthermore, there is significant heterogeneity between study protocols, including the short median follow-up, given that tumor regrowth and distant metastasis may manifest at a later time point.

CONCLUSION

The majority of patients with tumor regrowth can be salvaged with definite surgery after "watch and wait." However, there is insufficient evidence to draw firm conclusions on the oncological safety of this approach; therefore, it is currently not the standard of care for locally advanced rectal cancer.

Phospho-ERK1/2 levels in cancer cell nuclei predict responsiveness to radiochemotherapy of rectal adenocarcinoma

Locally advanced rectal adenocarcinoma is treated with radiochemotherapy (RCT) before surgery. The response to RCT is heterogeneous and consensus regarding reliable predictors is lacking. Since the ERK pathway is implicated in radioprotection, we examined pretreatment biopsies from 52 patients by immunohistochemistry for phosphorylated ERK (pERK). Immunostaining for pERK was considerably enhanced by use of alkaline demasking. Nuclear staining occurred in both cancer cells and stromal cells. Blind-coded sections were scored by 2 independent investigators. In patients showing no residual tumor after RCT (TRG1), staining for pERK in cancer, but not stromal, cell nuclei was significantly weaker than in patients showing a poor RCT response (TRG1 vs TRG4: p = 0.0001). Nuclear staining for pERK predicted poor responders, as illustrated by receiver operating characteristic curves with an area under curve of 0.86 (p = 0.0007) and also predicted downstaging (area under curve: 0.76; p = 0.01). A number of controls documented the specificity of the optimized staining method and results were confirmed with another pERK antibody. Thus, staining for pERK in cancer cell nuclei can predict the response to RCT and may help spare poor responders this treatment. These results also raise the question whether inhibitors of ERK activation may serve as response modifiers of RCT.

Apparent Diffusion Coefficient Predicts Pathology Complete Response of Rectal Cancer Treated with Neoadjuvant Chemoradiotherapy

Objective

To evaluate the predictive value of the apparent diffusion coefficient (ADC) for pathologic complete response (pCR) to neoadjuvant chemoradiotherapy (NCRT) in locally advanced rectal cancer.

Methods

A total of 265 patients with rectal adenocarcinoma, whole Diffusion-Weighted MRI (DWI-MRI) images, clinically stage II to III (cT3-4 and/or cN+) and treated with NCRT followed by TME were screened. Fifty patients with pCR and another 50 patients without pCR with similar clinical charcacters and treatment regimens were selected for statistical analysis. All the patients’ pre-CRT and post-CRT average ADC values were calculated from the coefficient maps created by DWI-MRI and recorded independently. The difference in the ADC values between the pCR and non-pCR was analyzed by the Mann-Whitney U test. The cut-off ADC value of the receiver operating characteristic (ROC) curve with pCR was then established.

Results

The mean pre- and post-ADC values in all patients, and in pCR patients and non-pCR patients were 0.879±0.06 and 1.383±0.11, 0.859±0.04 and 1.440±0.10, 0.899±0.07 and 1.325±0.09 (×10^-3mm²/s), respectively. The difference between the pre- and post-ADC values in all patients, pCR patients, and non-pCR patients were considered to be statistically significant. The pre-ADC value was significantly lower in the pCR patients than in the non-pCR patients (p = 0.003), whereas the post-ADC values were significantly higher in the pCR patients than in the non-pCR patients. The percentage increase of the ADC value (ΔADC%) in the pCR and non-pCR patients were 68% and 48% respectively (p<0.001). The ROC curves of the cut-off value of the pre-CRT patient ADC value was 0.866×10^-3mm²/s. The AUC, sensitivity, specificity, PPV, NPV, and accuracy of diagnosing pCR were 0.670 (95% CI 0.563–0.777), 0.600, 0.640, 60%, 60%, and 60%, respectively. The cut-off value of ΔADC% was 58%. The corresponding AUC, sensitivity, specificity, PPV, NPV, and accuracy of diagnosing pCR were 0.856 (95% CI 0.783–0.930), 0.800, 0.760, 76.9%, 79.2%, and 78%, respectively.

Conclusions

DWI-MRI technology can be efficient for predicting pCR for LARC after NCRT. Although the mean pre-CRT ADC value and the ΔADC% are moderate predictors for pCR, the latter would be more accurate.

Predictive Response Value of Pre- and Postchemoradiotherapy Variables in Rectal Cancer: An Analysis of Histological Data

Background. Neoadjuvant chemoradiotherapy (nCRT) followed by curative surgery in locally advanced rectal cancer (LARC) improves pelvic disease control. Survival improvement is achieved only if pathological response occurs. Mandard tumor regression grade (TRG) proved to be a valid system to measure nCRT response. Potential predictive factors for Mandard response are analyzed. Materials and Methods. 167 patients with LARC were treated with nCRT and curative surgery. Tumor biopsies and surgical specimens were reviewed and analyzed regarding mitotic count, necrosis, desmoplastic reaction, and inflammatory infiltration grade. Surgical specimens were classified according to Mandard TRG. The patients were divided as "good responders" (Mandard TRG1-2) and "bad responders" (Mandard TRG3-5). According to results from our previous data, good responders have better prognosis than bad responders. We examined predictive factors for Mandard response and performed statistical analysis. Results. In univariate analysis, distance from anal verge and ten other postoperative variables related with nCRT tumor response had predictive value for Mandard response. In multivariable analysis only mitotic count, necrosis, and differentiation grade in surgical specimen had predictive value. Conclusions. There is a lack of clinical and pathological preoperative variables able to predict Mandard response. Only postoperative pathological parameters related with nCRT response have predictive value.

Cytokeratin 20 positive circulating tumor cells are a marker for response after neoadjuvant chemoradiation but not for prognosis in patients with rectal cancer

Background

Several studies have shown, that circulating tumor cells (CTC) have a negative prognostic value in colorectal cancer patients. Aim of this study was to evaluate the role of CTC in specifically rectal cancer patients regarding the influence on overall survival and to elucidate the impact of CTC in predicting response after chemoradiation (RCTX).

Methods

In this prospective monocentric study 267 patients with rectal cancer were included. Patients with locally advanced tumors were treated with RCTX followed by surgery. The primary endpoints were: Evaluation of CTC at the time of surgery and correlation with main tumor characteristics, response to neoadjuvant RCTX and overall survival (OS). CTC were detected in the blood using CK20 RT-PCR.

Results

Sixty-three patients were treated with neoadjuvant RCTX. In 46.8 % of the patients receiving neoadjuvant RCTX CTC were detected, which was significantly higher than in the group without RCTX (p = 0.002). Histopathologic regression after RCTX was evident in 27.8 % of the patients. In the subgroup of responders after RCTX we found CTC at a significantly lower rate than in non-responders (p = 0.03). No significant association was found between CTC detection and tumor characteristics and OS. The OS was significantly improved for responders compared to non-responders (p = 0.007).

Conclusions

Responders after neoadjuvant RCTX had a lower incidence of CTC compared to non-responders, which might be a result of effective systemic and local treatment prior to surgery. Interestingly, detection of CTC did not correlate with tumor stage and OS, which is in contrast to previous reports of patients with colon cancer.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1989-z) contains supplementary material, which is available to authorized users.

The value of F-18 fluorodeoxyglucose positron emission tomography/computed tomography in asymptomatic examinees with unexplained elevated blood carcinoembryonic antigen levels

PURPOSE

Cancer is still a clinical challenge, with many efforts invested in order to achieve timely detection. Unexplained elevated blood carcinoembryonic antigen levels are occasionally observed in an asymptomatic population and considered as a risk factor of cancers. The purpose of this study was to determine the validity of 18 F-fluorodeoxyglucose-positron emission tomography/computed tomography (F-18 FDG-PET/CT) for detecting cancer in an asymptomatic population with an unexplained elevation in blood carcinoembryonic antigen (CEA) levels.

METHODS

This retrospective study included a total of 1920 asymptomatic examinees conducted from August 2011 through September 2013. The participants underwent CEA assay and conventional medical imaging (CEA-conventional), or CEA assay and F-18 FDG-PET/CT (CEA-PET/CT). The validity of conventional medical imaging and CEA-PET/CT scanning for detecting cancer and early-stage cancer in an asymptomatic population with an unexplained elevation in blood CEA levels were evaluated.

RESULTS

Sensitivity, specificity, cancer detection rate, missed cancer detection rate, early-stage cancer detection rate, and early-stage cancer ratio using the CEA-PET/CT scanning were 96.6 %, 100 %, 10.4 %, 0.4 %, 3.7 %, and 34.5 %, respectively. In contrast, the corresponding values obtained using the conventional medical imaging were 50.6 % (P < 0.0001), 100 % (P > 0.9999), 50.6 % (P < 0.0001), 99.9 % (P = 0.055), 2.6 % (P < 0.0001), 2.5 % (P = 0.04), 0.7 % (P = 0.0004), and 14.5 % (P = 0.002), respectively.

CONCLUSION

The F-18 FDG-PET/CT scanning significantly improved the validity of the cancer detection program in the asymptomatic population with an unexplained elevation in CEA levels.

Biomarkers and Molecular Imaging as Predictors of Response to Neoadjuvant Chemoradiotherapy in Patients With Locally Advanced Rectal Cancer

Standard treatment of patients with locally advanced rectal cancer (LARC) includes neoadjuvant chemoradiotherapy (NCRT) followed by surgery. Tumor regression after NCRT varies substantially among individuals and pathological complete response is a known prognostic factor for LARC. The identification of a predictive model for response to chemoradiotherapy would help clinicians to identify patients who would probably benefit from multimodal treatment and to perform an early assessment of individual prognosis. Carcinoembryonic antigen has proven to be a good predictor of response in several clinical trials. Other widely studied predictive models in LARC include molecular biomarkers, analyzed at various levels and by different techniques, and molecular imaging, in particular magnetic resonance imaging and positron emission tomography/computed tomography. Although none of the studied markers have been approved in clinical practice, their evaluation in larger, prospective trials and in combined predictive models could be of use to define tailored therapeutic strategies.

Effectiveness of the apparent diffusion coefficient for predicting the response to chemoradiation therapy in locally advanced rectal cancer: a systematic review and meta-analysis

The efficacy of the different apparent diffusion coefficients (ADCs) in predicting different responses to preoperative chemoradiation therapy (CRT) in patients with locally advanced rectal cancer (LARC) is controversial. We did this meta-analysis to evaluate the efficacy of different ADCs predicting different responses to CRT in patients with LARC.We systematically searched the MEDLINE, Embase, and Cochrane Library databases for articles published from January 1, 1990, to June 3, 2014. Pooled estimates were calculated using a bivariate random-effects model for the ADCs before and after CRT (pre- and post-ADC), as well as the change between the pre- and post-ADC (ΔADC). The values of the 3 ADCs for judging different response endpoints, which were defined according to the tumor grading (TRG) system and downstaging of T (tumor) or N (nodal) stages (TN downstaging), were assessed.We included 16 studies with a total of 826 patients. The sensitivity, specificity, DOR, and AUC were 75% (95% CI 57%-87%), 70% (95% CI 50%-84%), 6.81 (95% CI 2.46-18.88), and 0.79 (95% CI 0.75-0.82), respectively, for the pre-ADC in predicting a good response; 76% (95% CI 63%-85%), 87% (95% CI 78%-92%), 20.68 (95% CI 11.76-36.39), and 0.89 (95% CI 0.86-0.91), respectively, for the post-ADC; and 78% (95% CI 65%-87%), 77% (95% CI 62%-87%), 11.82 (95% CI 4.65-30.04), and 0.84 (95% CI 0.81-0.87), respectively, for the ΔADC. The post-ADC demonstrated the highest specificity and DOR (P < 0.001), although sensitivity did not differ between the 3 types of ADC (P = 0.380, 0.192, and 0.214). For predicting a pathological complete response (pCR), the post-ADC had the highest specificity (P < 0.001and 0.030) but lowest sensitivity (P < 0.001). The ΔADC had the highest DOR; however, this difference was not statistically significant (P = 0.146).The ADC is a reliable and reproducible measure and could serve as a promising noninvasive tool for evaluating the response to CRT in patients with LARC; the post-ADC and ΔADC are particularly promising. The ΔADC had the highest diagnostic performance to predict a pCR compared with the pre-ADC and post-ADC. The value of the ADCs to predict T or N downstaging requires further investigation.