MRI-based radiomic nomogram for predicting disease-free survival in patients with locally advanced rectal cancer

PURPOSE

Individual prognosis assessment is of paramount importance for treatment decision-making and active surveillance in cancer patients. We aimed to propose a radiomic model based on pre- and post-therapy MRI features for predicting disease-free survival (DFS) in locally advanced rectal cancer (LARC) following neoadjuvant chemoradiotherapy (nCRT) and subsequent surgical resection.

METHODS

This retrospective study included a total of 126 LARC patients, which were randomly assigned to a training set (n = 84) and a validation set (n = 42). All patients underwent pre- and post-nCRT MRI scans. Radiomic features were extracted from higher resolution T2-weighted images. Pearson correlation analysis and ANOVA or Relief were utilized for identifying radiomic features associated with DFS. Pre-treatment, post-treatment, and delta radscores were constructed by machine learning algorithms. An individualized nomogram was developed based on significant radscores and clinical variables using multivariate Cox regression analysis. Predictive performance was evaluated by the C-index, calibration curve, and decision curve analysis.

RESULTS

The results demonstrated that in the validation set, the clinical model including pre-surgery carcinoembryonic antigen (CEA), chemotherapy after radiotherapy, and pathological stage yielded a C-index of 0.755 (95% confidence interval [CI]: 0.739-0.771). While the optimal pre-, post-, and delta-radscores achieved C-indices of 0.724 (95%CI: 0.701-0.747), 0.701 (95%CI: 0.671-0.731), and 0.625 (95%CI: 0.589-0.661), respectively. The nomogram integrating pre-surgery CEA, pathological stage, alongside pre- and post-nCRT radscore, obtained the highest C-index of 0.833 (95%CI: 0.815-0.851). The calibration curve and decision curves exhibited good calibration and clinical usefulness of the nomogram. Furthermore, the nomogram categorized patients into high- and low-risk groups exhibiting distinct DFS (both P < 0.0001).

CONCLUSIONS

The nomogram incorporating pre- and post-therapy radscores and clinical factors could predict DFS in patients with LARC, which helps clinicians in optimizing decision-making and surveillance in real-world settings.

Predicting the risk of distant metastasis in patients with locally advanced rectal cancer using model based on pre-treatment T2WI-based radiomic features plus postoperative pathological stage

Objective

To assess the prognostic value of a model based on pre-treatment T2WI-based radiomic features and postoperative pathological staging in patients with locally advanced rectal cancer who have undergone neoadjuvant chemoradiotherapy.

Methods

Radiomic features were derived from T2WI, and a radiomic signature (RS) was established and validated for the prediction of distant metastases (DM). Subsequently, we designed and validated a nomogram model that combined the radiomic signature and postoperative pathological staging for enhanced DM prediction. Performance measures such as the concordance index (C-index) and area under the curve (AUC) were computed to assess the predictive accuracy of the models.

Results

A total of 260 patients participated in this study, of whom 197 (75.8%) were male, and the mean age was 57.2 years with a standard deviation of 11.2 years. 15 radiomic features were selected to define the radiomic signature. Patients with a high-risk radiomic signature demonstrated significantly shorter distant metastasis-free survival (DMFS) in both the development and validation cohorts. A nomogram, incorporating the radiomic signature, pathological T stage, and N stage, achieved an area under the curve (AUC) value of 0.72 (95% CI, 0.60-0.83) in the development cohort and 0.83 (95% CI, 0.73-0.92) in the validation cohort.

Conclusion

A radiomic signature derived from T2WI-based radiomic features can effectively distinguish patients with varying risks of DM. Furthermore, a nomogram integrating the radiomic signature and postoperative pathological stage proves to be a robust predictor of DMFS.

Prognostic Factors Among Colonic Adenocarcinomas Invading Into the Muscularis Propria

Depth of invasion through the intestinal wall, categorized as primary tumor stage (pT), is an important prognostic factor in colorectal cancer. However, additional variables that may affect clinical behavior among tumors involving the muscularis propria (pT2) have not been examined at length. We evaluated 109 patients with pT2 colonic adenocarcinomas (median age: 71 y, interquartile range: 59 to 79 y) along various clinicopathologic parameters, including invasion depth, regional lymph node involvement, and disease progression after resection. Tumors extending to the outer muscularis propria (termed pT2b) were associated in multivariate analysis with older patient age (P=0.04), larger tumor size (P<0.001), higher likelihood of lymphovascular invasion (LVI; P=0.03) and higher lymph node stage (pN; P=0.04), compared with tumors limited to the inner muscle layer (pT2a), and LVI was the single most important variable predicting regional lymph node metastasis at resection in these tumors (P=0.001). The Kaplan-Meier analysis during a median clinical follow-up of 59.7 months (interquartile range: 31.5 to 91.2) revealed that disease progression was more likely in pT2 tumors that exhibited, at the time of staging: size >2.5 cm (P=0.039), perineural invasion (PNI; P=0.047), high-grade tumor budding (P=0.036), higher pN stage (P=0.002), and distant metastasis (P<0.001). Proportional hazards (Cox) regression identified high-grade tumor budding (P=0.02) as independently predicting shorter progression-free survival in pT2 tumors. Finally, among cases that would not ordinarily be candidates for adjuvant treatment (ie, pT2N0M0), the presence of high-grade tumor budding was significantly associated with disease progression (P=0.04). These data suggest that, during the diagnosis of pT2 tumors, pathologists may wish to pay particular attention and ensure adequate reporting of certain variables such as tumor size, depth of invasion within the muscularis propria (ie, pT2a vs. pT2b), LVI, PNI, and, especially, tumor budding, as these may affect clinical treatment decisions and proper patient prognostication.

The percentage of mesorectal infiltration as a prognostic factor after curative surgery for pT3 rectal cancer

AIM

The aim of this study is to evaluate the prognostic value of a novel variable - the percentage of mesorectal infiltration (PMI) - in pT3 rectal cancer.

METHOD

A cohort of 241 patients with pT3 rectal adenocarcinoma, operated on between February 2002 and May 2019, was selected for the analysis. Data concerning patient, treatment and tumour characteristics were collected. The depth of mesorectal infiltration (DMI) and the distance between the deepest invasion and the circumferential resection margin (CRM) were measured. The PMI was calculated using a formula combining these parameters.

RESULTS

Neoadjuvant therapy was administered in 33.2% of cases. A complete mesorectal excision was achieved in 74% of patients. The CRM was affected in 24 patients (9.9%). The 5-year actuarial local recurrence (LR), overall recurrence (OR) and overall survival (OS) rates were 7.5%, 22.9% and 72.4%, respectively. The PMI was significantly associated with worse oncological outcomes regarding LR (p = 0.009), OR (p = 0.001) and OS (p = 0.016) rates. A cut-off value of PMI >60% had the highest specificity (80%) for LR (p = 0.026), OR (p = 0.04) and OS (p = 0.07).

CONCLUSION

The PMI has an adverse prognostic impact on the oncological results following surgery for pT3 rectal cancer. It allows prediction of the risk of both LR and distant recurrence with higher accuracy than the DMI or the distance to the CRM. A PMI >60% may be used as a cut off value while subclassifying pT3 rectal tumours. It may influence decision-making while establishing adjuvant treatment and the follow-up schedule.

Proposal of a T3 Subclassification for Colon Carcinoma

The TNM classification system is one of the most important factors determining prognosis for cancer patients. In colorectal cancer, the T category reflects the depth of tumor invasion. T3 is defined by a tumor that invades through the muscularis propria into pericolorectal tissues. The data of 1047 patients with complete mesocolic excision were analyzed. The depth of invasion beyond the outer border of the muscularis propria into the subserosa or into nonperitonealized pericolic tissue was measured and categorized in 655 pT3 patients: pT3a (≤1 mm), pT3b,c (>1−15 mm) and pT3d (>15 mm). The prognosis of these categories was compared. Five-year distant metastasis increased significantly from pT3a (5.7%) over pT3b,c (17.7%) to pT3d (37.2%; p = 0.001). There was no difference between pT2 (5.3%) and pT3a or between pT3d and pT4a (42.1%) or pT4b (33.7%). The 5-year disease-free survival decreased significantly from pT3a (77.4%) over pT3b,c (65.4%) to pT3d (50.1%; p = 0.015). No significant difference was found between pT2 (80.5%) and pT3a or between pT3d and pT4a (43.9%; p = 0.296) or pT4b (53.4%). The prognostic inhomogeneity in pT3 colon carcinoma has been demonstrated. A three-level subdivision of T3 for colon carcinoma in the TNM system into T3a (≤1 mm), T3b (>1−15 mm), and T3c (>15 mm) is recommended.

pT3 colorectal cancer revisited: a multicentric study on the histological depth of invasion in more than 1000 pT3 carcinomas-proposal for a new pT3a/pT3b subclassification

Background

Pathological TNM staging (pTNM) is the strongest prognosticator in colorectal carcinoma (CRC) and the foundation of its post-operative clinical management. Tumours that invade pericolic/perirectal adipose tissue generally fall into the pT3 category without further subdivision.

Methods

The histological depth of invasion into the pericolic/perirectal fat was digitally and conventionally measured in a training cohort of 950 CRCs (Munich). We biostatistically calculated the optimal cut-off to stratify pT3 CRCs into novel pT3a (≤3 mm)/pT3b (>3 mm) subgroups, which were then validated in two independent cohorts (447 CRCs, Bayreuth/542 CRCs, Mainz).

Results

Compared to pT3a tumours, pT3b CRCs showed significantly worse disease-specific survival, including in pN0 vs pN+ and colonic vs. rectal cancers (DSS: P < 0.001, respectively, pooled analysis of all cohorts). Furthermore, the pT3a/pT3b subclassification remained an independent predictor of survival in multivariate analyses (e.g. DSS: P < 0.001, hazard ratio: 4.41 for pT3b, pooled analysis of all cohorts). While pT2/pT3a CRCs showed similar survival characteristics, pT3b cancers remained a distinct subgroup with dismal survival.

Discussion

The delineation of pT3a/pT3b subcategories of CRC based on the histological depth of adipose tissue invasion adds valuable prognostic information to the current pT3 classification and implementation into current staging practices of CRC should be considered.

Prognostic significance of pathological sub-classification of pT3 rectal cancer

PURPOSE

Patients with pT3 rectal cancer represent a heterogeneous prognostic group. A more accurate histological sub-classification of pT status has been suggested as an improvement of the TNM staging system. The aim of the study was to evaluate the prognostic implication of a histopathologic sub-classification of pT3 rectal cancer.

METHODS

In this retrospective single-center study, pT3 rectal cancer patients who underwent surgery from January 2000 to December 2018 were evaluated. The maximum depth of tumor invasion beyond the muscularis propria was recorded. A ROC curve identified the best prognostic cutoff value to classify patients in two prognostic groups. Survival curves were estimated by the Kaplan-Meier method, and univariate and multivariate analyses with the Cox regression model were used to find independent factors influencing survival.

RESULTS

Overall, 203 patients were included. Four millimeters was identified as the best cutoff value: 82 patients showed a depth of invasion < 4 mm (group A) and 121 ≥ 4 mm (group B). Both the estimated 5-year OS and DFS were statistically better in group A than in group B (OS: 83.9% vs 62.2%, p < 0.01; DFS: 78.3% vs 40.6%, p < 0.01). The depth of tumor invasion was an independent risk factor for OS (HR 2.25, 95% CI 1.26-3.99, p = 0.006) and DFS (HR 2.30, 95% CI 1.40-3.78, p = 0.001).

CONCLUSION

Our findings suggest that a sub-classification of pT3 rectal cancer, based on the depth of tumor invasion, should be considered to be introduced in the TNM staging system.

Radiomics Features at Multiparametric MRI Predict Disease-Free Survival in Patients With Locally Advanced Rectal Cancer

OBJECTIVE

To investigate the potential value of radiomics features based on preoperative multiparameter MRI in predicting disease-free survival (DFS) in patients with local advanced rectal cancer (LARC).

METHODS

We identified 234 patients with LARC who underwent preoperative MRI, including T2-weighted, diffusion kurtosis imaging, and contrast enhanced T1-weighted. All patients were randomly divided into the training (n = 164) and validation (n = 70) cohorts. 414 features were extracted from the tumor from above sequences and the radiomics signature was then generated, mainly based on feature stability and Cox proportional hazards model. Two models, integrating pre- and postoperative variables, were constructed to validate the radiomics signatures for DFS estimation.

RESULTS

The radiomics signature, composed of six DFS-related features, was significantly associated with DFS in the training and validation cohorts (both p < 0.001). The radiomics signature and MR-defined extramural venous invasion (mrEMVI) were identified as the independent predictor of DFS both in the pre- and postoperative models. In both cohorts, the two radiomics-based models exhibited better prediction performance (C-index ≥0.77, all p < 0.05) than the corresponding clinical models, with positive net reclassification improvement and lower Akaike information criterion (AIC). Decision curve analysis also confirmed their clinical usefulness. The radiomics-based models could categorize LARC patients into high- and low-risk groups with distinct profiles of DFS (all p < 0.05).

CONCLUSION

The proposed radiomics models with pre- and postoperative features have the potential to predict DFS, and may provide valuable guidance for the future individualized management in patients with LARC.

Texture Analysis in the Assessment of Rectal Cancer: Comparison of T2WI and Diffusion-Weighted Imaging

Texture analysis (TA) techniques derived from T2-weighted imaging (T2WI) and apparent diffusion coefficient (ADC) maps of rectal cancer can both achieve good diagnosis performance. This study was to compare TA from T2WI and ADC maps between different pathological T and N stages to confirm which TA analysis is better in diagnosis performance. 146 patients were enrolled in this study. Tumor TA was performed on every patient's T2WI and ADC maps, respectively; then, skewness, kurtosis, uniformity, entropy, energy, inertia, and correlation were calculated. Our results demonstrated that those significant different parameters derived from T2WI had better diagnostic performance than those from ADC maps in differentiating pT3b-4 and pN1-2 stage tumors. In particular, the energy derived from T2WI was an optimal parameter for diagnostic efficiency. High-resolution T2WI plays a key point in the local stage of rectal cancer; thus, TA derived from T2WI may be a more useful tool to aid radiologists and surgeons in selecting treatment.

MRI-detected extramural venous invasion of rectal cancer: Multimodality performance and implications at baseline imaging and after neoadjuvant therapy

MRI is routinely used for rectal cancer staging to evaluate tumor extent and to inform decision-making regarding surgical planning and the need for neoadjuvant and adjuvant therapy. Extramural venous invasion (EMVI), which is intravenous tumor extension beyond the rectal wall on histopathology, is a predictor for worse prognosis. T2-weighted images (T2WI) demonstrate EMVI as a nodular-, bead-, or worm-shaped structure of intermediate T2 signal with irregular margins that arises from the primary tumor. Correlative diffusion-weighted images demonstrate intermediate to high signal corresponding to EMVI, and contrast enhanced T1-weighted images demonstrate tumor signal intensity in or around vessels. Diffusion-weighted and post contrast images may increase diagnostic performance but decrease inter-observer agreement. CT may also demonstrate obvious EMVI and is potentially useful in patients with a contraindication for MRI. This article aims to review the spectrum of imaging findings of EMVI of rectal cancer on MRI and CT, to summarize the diagnostic accuracy and inter-observer agreement of imaging modalities for its presence, to review other rectal neoplasms that may cause EMVI, and to discuss the clinical significance and role of MRI-detected EMVI in staging and restaging clinical scenarios.

"Rectal cancer survival: A retrospective analysis of MRI features and their association with prognosis"

PURPOSE

To assess rectal cancer aggressiveness using magnetic resonance (MR) imaging features and to investigate their relationship with patient prognosis.

MATERIALS AND METHODS

Clinical information and Pelvic MR scans of 106 consecutive patients with primary rectal cancer (RC) were analyzed. Clinical symptoms, age, sex, tumor location, and patient´s survival were recorded. The variables investigated by MR were: depth or mural/extramural tumor involvement, distance to mesorectal margin, lymph node involvement, vascular, peritoneal or sphincter complex infiltration. The association between imaging features and disease-free survival (DFS) was also assessed using a Kaplan-Meier model. Differences between survival curves were tested for significance using the Mantel-Cox LogRank test.

RESULTS

The final study population was 106 patients (65 males, 41 females). The median age was 69.5 years (range, 39-92 years). No significant differences were found between death risk and sex, age or tumor location (p>0,05). However, the relative risk (RR) of tumor mortality increased significantly with the presence of the variables: vascular infiltration (×5), T4 tumors (× 4.57), N2 lymph node involvement (more than 3 affected nodes × 4.11) and mesorectal fascia involvement (× 3,77).

CONCLUSION

Tumor extension, number of pathological lymph nodes, mesorectal fascia involvement and vascular infiltration values obtained on initial MR imaging staging showed a significant difference for disease-free survival in RC at six years of control.

Evaluation of the Extent of Mesorectal Invasion and Mesorectal Fascia Involvement in Patients with T3 Rectal Cancer With 2-D and 3-D Transrectal Ultrasound: A Pilot Comparison Study With Magnetic Resonance Imaging Findings

The aim of this study was to determine the value of 2-D and 3-D transrectal ultrasound (TRUS) in assessing the extent of mesorectal invasion (EMI) and mesorectal fascia involvement (MRF+) in patients with T3 rectal tumours. We retrospectively evaluated 80 patients with T3 stage rectal cancer who were pre-operatively evaluated by 2-D and 3-D TRUS before neoadjuvant chemoradiotherapy by using magnetic resonance imaging (MRI) as a reference standard. The T3 stage was subdivided into T3 ab (EMI ≤5 mm) and T3 cd (EMI >5 mm). The consistency assessment of the T3 sub-staging and MRF+ was compared between 2-D and 3-D TRUS using Cohen's kappa statistic. The concordance of the T3 sub-staging based on EMI was excellent between the 3-D TRUS and MRI (κ = 0.84) and good between the 2-D TRUS and MRI (κ = 0.67). For the assessment of MRF+ (κ = 0.82), 3-D TRUS and MRI showed excellent concordance. The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of 3-D TRUS for MRF+ assessment was 95.3%, 86.5%, 89.1% and 94.1%, respectively. The agreement between 3-D TRUS and MRI for the assessment of T3 sub-staging and MRF status was better in low rectal cancer (both κ = 0.85) than in middle (κ = 0.79 and 0.77) rectal cancer. Compared with MRI, 3-D TRUS has more advantages in the sub-staging of T3 rectal cancer and the assessment of MRF+ than those of 2-D TRUS, especially in low rectal cancer. For patients with T3 rectal cancer, 3-D TRUS may well complement MRI for selecting the appropriate treatment.

Prognostic value of multiparametric MRI-based radiomics model: Potential role for chemotherapeutic benefits in locally advanced rectal cancer

BACKGROUND AND PURPOSE

We aimed to develop a radiomics model for the prediction of survival and chemotherapeutic benefits using pretreatment multiparameter MR images and clinicopathological features in patients with locally advanced rectal cancer (LARC).

MATERIALS AND METHODS

186 consecutive patients with LARC underwent feature extraction from the whole tumor on T2-weighted, contrast enhanced T1-weighted, and ADC images. Feature selection was based on feature stability and the Boruta algorithm. Radiomics signatures for predicting DFS (disease-free survival) were then generated using the selected features. Combining clinical risk factors, a radiomics nomogram was constructed using Cox proportional hazards regression model. The predictive performance was evaluated by Harrell's concordance indices (C-index) and time-independent receiver operating characteristic (ROC) analysis.

RESULTS

Four features were selected to construct the radiomics signature, significantly associated with DFS (P < 0.001). The radiomics nomogram, incorporating radiomics signature and two clinicopathological variables (pN and tumor differentiation), exhibited better prediction performance for DFS than the clinicopathological model, with C-index of 0.780 (95%CI, 0.718-0.843) and 0.803 (95%CI, 0.717-0.889) in the training and validation cohorts, respectively. The radiomics nomogram-defined high-risk group had a shorter DFS, DMFS, and OS than those in the low-risk group (all P < 0.05). Further analysis showed that patients with higher nomogram-defined score exhibited a favorable response to adjuvant chemotherapy (AC) while the low-risk could not.

CONCLUSION

This study demonstrated that the newly developed pretreatment multiparameter MRI-based radiomics model could serve as a powerful predictor of prognosis, and may act as a potential indicator for guiding AC in patients with LARC.

Predicting distant metastasis and chemotherapy benefit in locally advanced rectal cancer

Distant metastasis (DM) is the main cause of treatment failure in locally advanced rectal cancer. Adjuvant chemotherapy is usually used for distant control. However, not all patients can benefit from adjuvant chemotherapy, and particularly, some patients may even get worse outcomes after the treatment. We develop and validate an MRI-based radiomic signature (RS) for prediction of DM within a multicenter dataset. The RS is proved to be an independent prognostic factor as it not only demonstrates good accuracy for discriminating patients into high and low risk of DM in all the four cohorts, but also outperforms clinical models. Within the stratified analysis, good chemotherapy efficacy is observed for patients with pN2 disease and low RS, whereas poor chemotherapy efficacy is detected in patients with pT1-2 or pN0 disease and high RS. The RS may help individualized treatment planning to select patients who may benefit from adjuvant chemotherapy for distant control.

Optimising functional outcomes in rectal cancer surgery

Background

By improved surgical technique such as total mesorectal excision (TME), multimodal treatment and advances in imaging survival and an increased rate of sphincter preservation have been achieved in rectal cancer surgery. Minimal-invasive approaches such as laparoscopic, robotic and transanal-TME (ta-TME) enhance recovery after surgery. Nevertheless, disorders of bowel, anorectal and urogenital function are still common and need attention.

Purpose

This review aims at exploring the causes of dysfunction after anterior resection (AR) and the accordingly preventive strategies. Furthermore, the indication for low AR in the light of functional outcome is discussed. The last therapeutic strategies to deal with bowel, anorectal, and urogenital disorders are depicted.

Conclusion

Functional disorders after rectal cancer surgery are frequent and underestimated. More evidence is needed to define an indication for non-operative management or local excision as alternatives to AR. The decision for restorative resection should be made in consideration of the relevant risk factors for dysfunction. In the case of restoration, a side-to-end anastomosis should be the preferred anastomotic technique. Further high-evidence clinical studies are required to clarify the benefit of intraoperative neuromonitoring. While the function of ta-TME seems not to be superior to laparoscopy, case-control studies suggest the benefits of robotic TME mainly in terms of preservation of the urogenital function. Low AR syndrome is treated by stool regulation, pelvic floor therapy, and transanal irrigation. There is good evidence for sacral nerve modulation for incontinence after low AR.

[Selection criteria for neoadjuvant chemoradiotherapy of rectal cancer : Neoadjuvant therapy even for locally advanced colon cancer?]

During the last two decades a neoadjuvant treatment concept has been established for an increasing number of malignant tumors of the gastrointestinal tract; however, these concepts are still subject to a constant change concerning the indications and type of treatment. A prime example for this is rectal cancer. The rate of local recurrence in particular was significantly reduced by neoadjuvant therapy but until now it has not been possible to validly show an improvement in overall or disease-free survival. At the beginning of the millennium it was recommended to treat every rectal carcinoma in UICC stages II and III with neoadjuvant therapy, independent of the height localization. In the meantime this has increasingly been relativized and only locally advanced tumors of the middle and lower thirds of the rectum should be pretreated, whereas tumors of the upper third of the rectum should basically be treated in the same way as colon cancer. It is to be expected that there will be further differentiation concerning the indications in this context in the future mainly based on a preoperative magnetic resonance imaging (MRI) examination. At the same time, initial studies for colon cancer show that neoadjuvant chemotherapy can be beneficial and that an optimized computed tomography (CT) scan can be a worthwhile tool with respect to pretherapeutic stratification of patients.

Pathological Tumor Regression Grade Classifications in Gastrointestinal Cancers: Role on Patients' Prognosis

Preoperative chemotherapy or combined radiotherapy and chemotherapy (CRT), followed by surgery, represents the standard approach for locally advanced esophageal, gastric, and rectal carcinomas. To adequately evaluate the effects of neoadjuvant CRT in the resection specimens, several histopathologic tumor regression grade (TRG) scoring systems have been introduced into clinical practice. The primary goal of these TRG systems relies on a correct prognostic stratification of patients in the attempt to help clinical decision-making and influence surgical strategies, postoperative adjuvant therapies, and surveillance intensity. However, most TRG systems suffer from poor reproducibility and low interobserver concordance rates. Many efforts have been made in the identification of alternative, robust, simple, and universally accepted TRG scoring systems, which would help in the comparison of different treatment strategies and in the standardization of multimodal therapies. The aim of this review is to analyze the most commonly used TRG systems in gastrointestinal cancers highlighting their pitfalls and usefulness, depending on the tumor type.

Current concepts in imaging for local staging of advanced rectal cancer

Imaging of rectal cancer has an increasingly pivotal role in the diagnosis, staging, and treatment stratification of patients with the disease. This is particularly true for advanced rectal cancers where magnetic resonance imaging (MRI) findings provide essential information that can change treatment. In this review we describe the rationale for the current imaging standards in advanced rectal cancer for both morphological and functional imaging on the baseline staging and reassessment studies. In addition the clinical implications and future methods by which radiologists may improve these are outlined relative to TNM8.

Prognostic subdivision of pT2 rectal carcinomas

PURPOSE

The aim of the present study is to explore the prognostic impact of a subdivision of pT2 by the depth of invasion into the muscularis propria in rectal carcinomas.

METHODS

Data from 269 consecutive patients with rectal carcinoma treated with primary tumor resection and lymph node dissection between 1986 and 2012 were analyzed with respect to locoregional and distant recurrence, disease-free survival, and overall survival. The depth of invasion into the muscularis propria of pT2 carcinomas was categorized by the pathologist into two groups: pT2a, invasion into the inner half of the muscularis propria; pT2b, invasion into the outer half of the muscularis propria.

RESULTS

One hundred nineteen of the 269 patients (44.2%) were classified pT2a and 150 patients (55.8%) were classified pT2b. In univariate analysis, significant differences between pT2a and pT2b carcinomas were found for locoregional recurrences (5-year rates 5.3 vs 14.0%; p = 0.025), distant metastases (14.1 vs 18.7%; p = 0.026), disease-free survival (78.2 vs 62.5%; p = 0.022), and overall survival (87.4 vs 72.5%; p = 0.013). In multivariate Cox regression analysis, the pT2 subdivision was found to be an independent risk factor for locoregional recurrence (hazard ratio 2.6; p = 0.023), disease-free survival (HR 1.4; p = 0.022), and overall survival (HR 1.5; p = 0.020), but only marginally for distant metastasis (HR 1.7; p = 0.083). Other independent prognostic factors were lymph node status, lymphatic invasion, and grading.

CONCLUSIONS

The depth of invasion into the muscularis propria is an independent prognostic factor for pT2 rectal carcinomas that will support decision-making for preoperative, surgical, and postoperative treatment.

Novel radiomic signature as a prognostic biomarker for locally advanced rectal cancer

BACKGROUND

Locally advanced rectal cancer (LARC) patient stratification by clinicoradiologic factors may yield variable results. Therefore, more efficient prognostic biomarkers are needed for improved risk stratification of LARC patients, personalized treatment, and prognostication.

PURPOSE/HYPOTHESIS

To compare the ability of a radiomic signature to predict disease-free survival (DFS) with that of a clinicoradiologic risk model in individual patients with LARC.

STUDY TYPE

Retrospective study.

POPULATION

In all, 108 consecutive patients (allocated to a training and validation set with a 1:1 ratio) with LARC treated with neoadjuvant chemoradiotherapy (nCRT) followed by total mesorectal excision (TME).

FIELD STRENGTH/SEQUENCE

Axial 3D LAVA multienhanced MR sequence at 3T.

ASSESSMENT

ITK-SNAP software was used for manual segmentation of 3D pre-nCRT MR images. All manual tumor segmentations were performed by a gastrointestinal tract radiologist, and validated by a senior radiologist. The clinicoradiologic risk factors with potential prognostic outcomes were identified in univariate analysis based on the Cox regression model for the whole set. The results showed that ypT, ypN, EMVI, and MRF were potential clinicoradiologic risk factors. Interestingly, only ypN and MRF were identified as independent predictors in multivariate analysis based on the Cox regression model.

STATISTICAL TESTS

A radiomic signature based on 485 3D features was generated using the least absolute shrinkage and selection operator (LASSO) Cox regression model. The association of the radiomic signature with DFS was investigated by Kaplan-Meier survival curves. Survival curves were compared by the log-rank test. Three models were built and assessed for their predictive values, using the Harrell concordance index and integrated time-dependent area under the curve.

RESULTS

The novel radiomic signature stratified patients into low- and high-risk groups for DFS in the training set (hazard ratio [HR] = 6.83; P < 0.001), and was successfully validated in the validation set (HR = 2.92; P < 0.001). The model combining the radiomic signature and clinicoradiologic findings had the best performance (C index = 0.788, 95% confidence interval [CI] 0.72-0.86; integrated time-dependent area under the curve of 0.837 at 3 years).

DATA CONCLUSION

The novel radiomic signature could be used to predict DFS in patients with LARC. Furthermore, combining this radiomic signature with clinicoradiologic features significantly improved the ability to estimate DFS (P = 0.001, 0.005 in training set and in validation set, respectively), and may help guide individualized treatment in such patients.

LEVEL OF EVIDENCE

3 Technical Efficacy: Stage 5 J. Magn. Reson. Imaging 2018.

How Should Imaging Direct/Orient Management of Rectal Cancer?

Modern rectal cancer management is dependent on preoperative staging, and radiological assessment is a crucial part of this process. Imaging must provide sufficient information to guide preoperative decision-making that is reliable and reproducible. Different methods have been used for local staging; however, magnetic resonance imaging (MRI) has shown to be the most reliable tool for this purpose. MRI offers prognostic information about the patients and guides the decision between neoadjuvant treatment and total mesorectal excision alone. Also, not only the initial staging but also restaging by MRI can provide significant information regarding tumor response that is essential when considering alternative approaches.

Does the depth of mesorectal invasion have prognostic significance in patients with ypT3 lower rectal cancer treated with preoperative chemoradiotherapy?

PURPOSE

The prognostic significance of the depth of mesorectal invasion (DMI) in patients with ypT3 rectal cancer who undergo preoperative chemoradiotherapy (CRT) is unclear. The purpose of this study was to evaluate the prognostic significance of DMI in ypT3 rectal cancer.

METHODS

A total of 168 (y)pT3 patients were evaluated, of whom 93 received preoperative CRT and 75 underwent surgery alone. Patients were subdivided into two groups according to the DMI (T3ab = DMI ≤5 mm and T3cd = DMI >5 mm). Oncologic outcomes were compared between the T3ab and T3cd groups and the ypT3ab and ypT3cd groups.

RESULTS

Relapse-free survival was significantly different between the pT3ab and pT3cd groups (74.1 vs 38.5%, P = 0.0192) but not between the ypT3ab and ypT3cd groups (65.9 vs 61.5%, P = 0.513). Multivariate analysis showed that DMI was an independent predictor of recurrence in pT3 patients (hazard ratio [HR] = 2.980, 95% confidence interval [CI] 1.227-7.025; P = 0.0169) and that ypN+ was an independent predictor of recurrence in ypT3 patients (HR = 3.487, 95% CI 1.570-8.827; P = 0.0016).

CONCLUSIONS

DMI was not a significant predictive factor for recurrence in patients with ypT3 rectal cancer who underwent preoperative CRT, and ypN+ was the only independent predictive factor for recurrence.

The degree of extramural spread of T3 rectal cancer: an appeal to the American Joint Committee on Cancer

The T3 category of the TNM classification includes over 60% of all rectal tumours and encompasses the greatest variance in cancer-specific end-points than any other T category. The most recent edition of the cancer staging handbook of the American Joint Committee on Cancer (AJCC) dated 2010 does not divide T3 tumours into subgroups which reflect cancer-specific outcome more sensitively. The original aim of the present study was to review the literature to assess the influence of the degree of extramural extent of T3 rectal cancer on local recurrence and survival. An article written by the authors was accepted for publication but was withdrawn immediately after they became aware of the publication of the 4th edition of the TNM Supplement by the Union for International Cancer Control dated 2012, which was not accessible by the search system used. This article dealt with the subdivision of the T3 category although this was not included in the most up-to-date AJCC guidelines and was stated to be 'entirely optional'. Medline, PubMed and Cochrane Library searches were performed to identify all studies that investigated the degree of extramural spread and its relationship to survival and local recurrence. Twenty-two studies were identified of which 12 assessed the degree of histopathological extramural spread measured in millimetres. In 18 of the 22 studies the degree of extramural spread was a statistically significant prognostic factor for survival and local recurrence. Analysis of the studies indicated that the subdivision of category T3 rectal cancer into two subgroups of extramural spread ≤ 5 mm or more than 5 mm resulted in markedly different survival and local recurrence rates. The data were insufficient to allow validation of any greater subdivision. Measurement of the extent of extramural spread by MRI before any treatment agreed with the histopathological measurement in the surgical specimen to within 1 mm. The extent of extramural spread in T3 rectal cancer measured in millimetres is a powerful prognostic factor. A subdivision of T3 into T3a and T3b of less than or equal to or more than 5 mm appears to give the greatest discrimination of local recurrence and survival. Preoperative T3 subdivision by MRI has the same sensitivity as histopathological examination of the resected specimen. Given the clinical need for the pretreatment classification of the T3 category for oncological management planning, the evidence strongly indicates that the subdivision of the T3 category by MRI should be formally considered as part of the TNM staging system for rectal cancer.

FDG PET/CT Can Assess the Response of Locally Advanced Rectal Cancer to Neoadjuvant Chemoradiotherapy: Evidence From Meta-analysis and Systematic Review

INTRODUCTION

Neoadjuvant chemoradiotherapy (CRT) is indicated in locally advanced rectal adenocarcinoma where there is a high risk of local recurrence based on preoperative imaging. Optimal radiological assessment of CRT response is unknown, and metabolic assessment of the tumor has been suggested to gauge response before surgical resection.

PATIENTS AND METHODS

A systematic search of the MEDLINE database was performed using the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) statement to identify papers comparing pre- and post-CRT PET/CT in patients with locally advanced rectal adenocarcinoma with histopathological assessment of tumor regression. Papers were assessed with the QUADAS (Quality Assessment of Diagnostic Accuracy Studies) tool. Meta-analysis was performed for response index (RI) and SUVmax post-CRT.

RESULTS

Ten of 69 studies met inclusion criteria containing a total of 538 patients. Methodological quality was high with low heterogeneity. In all studies, post-CRT PET/CT showed a reduction in SUVmax and the RI irrespective of histological findings. Tumors confirmed to have regressed after CRT had a mean difference of 12.21% higher RI (95% confidence interval, 6.51-17.91; P < 0.00001) compared with nonresponders. Mean difference between pre- and post-CRT SUVmax groups was -2.48 (95% confidence interval, -3.06 to -1.89; P < 0.00001) with histopathological responders having a lower post-CRT SUVmax.

CONCLUSIONS

The available evidence suggests that PET/CT may be a useful addition to the current imaging modalities in the assessment of treatment response.

JOURNAL CLUB: Preoperative MRI Evaluation of Primary Rectal Cancer: Intrasubject Comparison With and Without Rectal Distention

OBJECTIVE

The aim of this study was to determine whether rectal distention influences the accuracy of MRI for tumor staging and for measuring of maximal extramural depth of tumor spread and distance between tumor and mesorectal fascia (MRF).

SUBJECTS AND METHODS

Fifty patients with rectal carcinoma underwent MRI before and after rectal distention. Both sets of MR images were reviewed by two radiologists. The scores for depiction of the mass (1-4 scale), T and N category, distance from normal rectal wall to MRF, maximal extramural depth of tumor spread, and distance between tumor and MRF were evaluated.

RESULTS

The visualization scores on MR images obtained with the rectum distended were significantly higher than those on images obtained without distention (90% vs 58% for score 4, p < 0.001). The accuracy of T category assessed on distended images was slightly higher than the accuracy on nondistended images (88.6% vs 84.1% for observer 1, 84.1% vs 81.8% for observer 2), but the accuracy of N category was stable. The distance between normal rectal wall and MRF was significantly less on distended images than on nondistended images (p < 0.05). However, there was no significant difference between nondistended and distended images for maximal extramural depth and distance between tumor and MRF (p > 0.05).

CONCLUSION

Rectal distention significantly improved visualization of tumors on MR images. It also improved T category assessment to some extent. Although the distance between normal rectal wall and MRF was significantly less with rectal distention than without rectal distention, maximal extramural depth and the distance between tumor and MRF did not vary significantly with or without rectal distention.

Five-year outcomes of preoperative chemoradiation for rectal carcinoma in Saudi population: single-institutional experience

OBJECTIVES

Preoperative chemoradiation (CRT) followed by surgery is the standard treatment for locally advanced rectal cancer (LARC). The outcomes of preoperative CRT in Saudi patients with LARC have not been widely studied. The study reports long-term outcomes after preoperative CRT followed by curative surgery in Saudi patients with LARC.

DESIGN AND SETTINGS

A retrospective, single-institutional study performed in the tertiary care oncology center in Saudi Arabia.

MATERIALS AND METHODS

A total of 154 out of 204 patients with LARC were treated with preoperative CRT and followed by surgery at the oncology center between September 2005 and November 2012. Data regarding the response rates, toxicity profile, locoregional control (LRC), distant metastasis control (DMC), overall survival (OS), and disease-free survival (DFS) rates were analyzed.

RESULTS

The median age of the study population was 56.6 years (range: 26-89). Predominant clinical stages were IIA (70 patients; 45.4%) and IIIB (49 patients; 31.8%). Majority of patients (79.8%) underwent a complete total mesorectal excision (TME). Complete pathological response (ypT0N0) was seen in 26 patients (16.8%). At 5 years, locoregional recurrence (LR) was reported in 12 patients (7.8%), and distant metastases were noted in 33 patients (21.4%). The 5-year cumulative LRC, DMC, OS, and DFS rates were 91%, 71.3%, 78%, and 64.8%, respectively. Stage, nodal status, circumferential margins, ypT0N0, and adjuvant chemotherapy were found to be important prognostic factors for DFS.

CONCLUSION

The results of preoperative CRT followed by surgery and adjuvant chemotherapy in Saudi population are comparable with international data.

Outcomes in locally advanced rectal cancer with highly selective preoperative chemoradiotherapy

BACKGROUND

This study compared outcomes after surgery alone for stage II/ III rectal cancer in a tertiary cancer unit versus highly selective use of preoperative chemoradiotherapy (CRT).

METHODS

This was a single-centre retrospective cohort study of consecutive patients receiving potentially curative surgery for stage II and III primary rectal cancer. CRT was given only for magnetic resonance imaging-predicted circumferential resection margin (CRM) involvement and nodal disease (at least N2). Primary endpoints were CRM involvement and local recurrence rates. Secondary endpoints were systemic recurrence and overall survival. Data were analysed by log rank test, and univariable and multivariable analysis.

RESULTS

Between 2002 and 2012, 363 patients were treated for rectal cancer. After applying exclusion criteria, 266 patients with stage II/III mid or low rectal cancer were analysed. Of these, 103 received neoadjuvant CRT and 163 proceeded directly to surgery, seven of whom required postoperative radiotherapy; the latter patients were included in the neoadjuvant CRT group for analysis. There was a significant difference in local recurrence between the CRT and surgery-alone groups (6·5 versus 0 per cent at 5 years; P = 0·040), but not in CRM involvement (7·2 versus 5·1 per cent; P = 0·470), 5-year systemic recurrence (37·2 versus 43·0 per cent; P = 0·560) and overall survival (64·2 versus 64·6 per cent; P = 0·628) rates. Metastatic disease developed more frequently in low rectal cancers (odds ratio 0·14; P < 0·001), regardless of whether neoadjuvant treatment was delivered.

CONCLUSION

Locally advanced rectal cancer does not necessarily require neoadjuvant CRT.