Locally advanced rectal cancer: qualitative and quantitative evaluation of diffusion-weighted magnetic resonance imaging in restaging after neoadjuvant chemo-radiotherapy

Combination of intravoxel incoherent motion histogram parameters and clinical characteristics for predicting response to neoadjuvant chemoradiation in patients with locally advanced rectal cancer

OBJECTIVE

To explore the value of histogram parameters derived from intravoxel incoherent motion (IVIM) for predicting response to neoadjuvant chemoradiation (nCRT) in patients with locally advanced rectal cancer (LARC).

METHODS

A total of 112 patients diagnosed with LARC who underwent IVIM-DWI prior to nCRT were enrolled in this study. The true diffusion coefficient (D), pseudo-diffusion coefficient (D*), and microvascular volume fraction (f) calculated from IVIM were recorded along with the histogram parameters. The patients were classified into the pathological complete response (pCR) group and the non-pCR group according to the tumor regression grade (TRG) system. Additionally, the patients were divided into low T stage (yp T0-2) and high T stage (ypT3-4) according to the pathologic T stage (ypT stage). Univariate logistic regression analysis was implemented to identify independent risk factors, including both clinical characteristics and IVIM histogram parameters. Subsequently, models for Clinical, Histogram, and Combined Clinical and Histogram were constructed using multivariable binary logistic regression analysis for the purpose of predicting pCR. The area under the receiver operating characteristic (ROC) curve (AUCs) was employed to evaluate the diagnostic performance of the three models.

RESULTS

The values of D_ kurtosis, f_mean, and f_ median were significantly higher in the pCR group compared with the non-pCR group (all P < 0.05). The value of D*_ entropy was significantly lower in the pCR group compared with the non-pCR group (P < 0.05). The values of D_ kurtosis, f_mean, and f_ median were significantly higher in the low T stage group compared with the high T stage group (all P < 0.05). The value of D*_ entropy was significantly lower in the low T stage group compared with the high T stage group (P < 0.05). The ROC curves indicated that the Combined Clinical and Histogram model exhibited the best diagnostic performance in predicting the pCR patients with AUCs, sensitivity, specificity, and accuracy of 0.916, 83.33%, 85.23%, and 84.82%.

CONCLUSIONS

The histogram parameters derived from IVIM have the potential to identify patients who have achieved pCR. Moreover, the combination of IVIM histogram parameters and clinical characteristics enhanced the diagnostic performance of IVIM histogram parameters.

Predictive value of mono-exponential and multiple mathematical models in locally advanced rectal cancer response to neoadjuvant chemoradiotherapy

PURPOSE

This prospective study aimed to assess the predictive value of mono-exponential and multiple mathematical diffusion-weighted imaging (DWI) models in determining the response to neoadjuvant chemoradiotherapy (nCRT) in patients with locally advanced rectal cancer (LARC).

METHODS

The study included 103 LARC patients scheduled for preoperative chemoradiotherapy between December 2021 and June 2023 Magnetic resonance imaging (MRI) scans were performed using a 3.0-T MR scanner, encompassing sagittal, axial, and oblique coronal T2-weighted images without fat saturation, along with DWI perpendicular to the rectum's long axis. Various DWI parameters, including apparent diffusion coefficient (ADC), stretched exponential model (SEM), continuous-time random-walk model (CTRW), and fractional-order calculus model (FROC), were measured. The pathologic complete response (pCR) rate and tumor downstaging (T-downstage) rate were determined.

RESULTS

After nCRT, SEM-α, SEM-DDC, CTRW-α, CTRW-β, CTRW-D, FROC-β, and ADC values were significantly higher in the pCR group compared to the non-pCR group (all P < 0.05). SEM-DDC, CTRW-α, CTRW-D, FROC-β, FROC-µ, and ADC values were significantly higher in the T-downstage group (ypT0-1) than in the non-T-downstage group (ypT2-4) (P < 0.05). The combination of CTRW (α + β + D) exhibited the best diagnostic performance for assessing pCR after nCRT (AUC = 0.840, P < 0.001). Pre-nCRT CTRW (α + β) demonstrated a predictive AUC of 0.652 (95%CI: 0.552-0.743), 90.3% sensitivity, and 43.1% specificity for pCR. Regarding T-downstage assessment after nCRT, the combination of CTRW (α + D) yielded the best diagnostic performance (AUC = 0.877, P = 0.048).

CONCLUSION

In LARC patients, imaging markers derived from CTRW show promise in predicting tumor response before nCRT and assessing pCR after nCRT.

A randomized phase 3 trial of total neoadjuvant therapy (induction chemotherapy, neoadjuvant chemoradiation, neoadjuvant chemotherapy, and surgery) vs. standard long-term chemoradiation therapy (neoadjuvant chemoradiation, surgery, and adjuvant chemotherapy) in locally advanced rectal cancer

Purpose

The management of rectal adenocarcinoma has evolved during the last decade, shifting from a conventional neoadjuvant chemoradiotherapy, surgery, and adjuvant chemotherapy in all cases to a total neoadjuvant approach, especially in locally advanced tumors when a sphincter-sparing surgery has been planned. However, the exact indications and the neoadjuvant regimen with the highest response remain unresolved. We aimed to assess whether administering neoadjuvant chemotherapy before and after preoperative chemoradiotherapy could increase the pathological complete response (pCR) rates.

Methods

We conducted a phase 3, multicenter, randomized trial at four hospitals in Iran. Adult patients with a newly diagnosed, biopsy-proven, locally advanced non-metastatic rectal adenocarcinoma with an ECOG performance status of 0-2 were randomly assigned (2:2) to either the total neoadjuvant treatment (TNT) or the standard-of-care groups using a block randomized design. Investigators and participants were not masked to treatment allocation and groups. The TNT group received neoadjuvant chemotherapy with FOLFOX6 (intravenous 85 mg/m2 oxaliplatin and 400 mg/m2 leucovorin, followed by intravenous 400 mg/m2 fluorouracil bolus and then continuous infusion at a dose of 2,400 mg/m2 over 46 h every 14 days for four cycles before and four cycles after chemoradiotherapy), chemoradiotherapy (50.4 Gy during 28 fractions and 800 mg/m2 concurrent oral capecitabine twice daily 5 days per week), and total mesorectal excision. The standard-of-care group received neoadjuvant chemoradiotherapy, total mesorectal excision, and adjuvant chemotherapy (eight cycles). The primary endpoint was the pathological complete response. Safety analyses were conducted on treated patients.

Results

Overall, 25 and 27 patients were enrolled in the TNT and standard-of-care groups, respectively. Both groups were similar in terms of gender, age, and tumor differentiation. The tumors in the standard-of-care group were significantly located closer to the anal verge compared with those in the TNT group (9.4 ± 3.7 cm in TNT vs. 6.8 ± 4 cm in standard, p = 0.02). A pCR was reached in 48% (12/25) and 25.9% (7/27) of patients in the TNT and standard-of-care groups, respectively (p = 0.4). The R0 resection rates were identical between the two groups (92% vs. 88.9%, p = 0.3). Moreover, the toxicity rates were similar between the two groups.

Conclusion

Our results showed that TNT is a safe and feasible treatment approach in patients with rectal cancer and may improve the overall pCR rate compared with standard treatment.

Clinical trial registration

https://irct.behdasht.gov.ir/trial/65666, identifier IRCT20220723055527N1.

Fractional order calculus model-derived histogram metrics for assessing pathological complete response to neoadjuvant chemotherapy in locally advanced rectal cancer

AIM

This study evaluates the value of diffusion fractional order calculus (FROC) model for the assessment of pathological complete response (pCR) after neoadjuvant chemoradiotherapy (nCRT) for locally advanced rectal cancer (LARC) by using histogram analysis derived from whole-tumor volumes.

MATERIALS AND METHODS

Ninety-eight patients were prospectively included. Every patient received MRI scans before and after nCRT using a 3.0-Tesla MRI machine. Parameters of the FROC model, including the anomalous diffusion coefficient (D), intravoxel diffusion heterogeneity (β), spatial parameter (μ), and the standard apparent diffusion coefficient (ADC), were calculated. Changes in median values (ΔX-median) and ratio (rΔX-median) were calculated. Receiver operating characteristic (ROC) curves were used for evaluating the diagnostic performance.

RESULTS

Pre-treatmentβ-10th percentile values were significantly lower in the pCR group compared to the non-pCR group (p < 0.001). The Δβ-median showed higher diagnostic accuracy (AUC = 0.870) and sensitivity (76.67 %) for predicting tumor response compared to MRI tumor regression grading (mrTRG) scores (AUC = 0.722; sensitivity = 90.0 %).

DISCUSSION

The use of FROC alongside comprehensive tumor histogram analysis was found to be practical and effective in evaluating the tumor response to nCRT in LARC patients.

MRI Tumor Regression Response to Neoadjuvant Chemotherapy Alone without Radiation for Rectal Adenocarcinoma

Background Neoadjuvant chemotherapy (NCT) is gaining acceptance for the management of locally advanced rectal cancer (LARC) in patients without negative prognostic factors. However, the value of MRI in evaluating tumor response after NCT remains unclear. Purpose To investigate the accuracy of MRI in assessing pathologic complete response in participants with LARC who underwent surgery after NCT without radiation. Materials and Methods A retrospective imaging substudy was conducted within two consecutive prospective clinical trials: the expanded phase II trial (from December 2017 to May 2021) and the COPEC trial (comparison of tumor response to two or four cycles of neoadjuvant chemotherapy alone, ongoing from August 2021). All included participants received four cycles of capecitabine combined with oxaliplatin (or CAPOX) before surgery. Three radiologists who were blinded to the clinicopathologic data independently evaluated the tumor response using five methods, namely, MR tumor regression grade (MR-TRG) alone, diffusion-weighted imaging (DWI) alone, DWI-modified MR-TRG (DWImodMR-TRG), MRI complete response, and radiologic neoadjuvant response score. With pathologic assessment serving as the reference standard, the positive and negative predictive values, sensitivity, specificity, and area under the receiver operating characteristic curve (AUC) were determined to evaluate the accuracy and performance of these models. The AUCs of the models were compared using the DeLong test. Results A total of 224 participants were included, comprising 119 from the expanded phase II trial (median age, 61 years [IQR, 53-67]; 89 male) and 105 from the COPEC trial (median age, 59 years [IQR, 53-67]; 65 male). MR-TRG, DWI, DWImodMR-TRG, MRI complete response, and the radiologic neoadjuvant response score were associated with pathologic complete response. DWImodMR-TRG achieved the highest AUC of 0.90 (95% CI: 0.85, 0.95), with a specificity of 89% (162 of 182) and a negative predictive value of 93% (162 of 174). Conclusion MRI-based models were accurate for determining pathologic complete response in participants with LARC following NCT. DWI improved the predictive performance of MRI-based assessment. © RSNA, 2024 Supplemental material is available for this article. See also the editorial by Santiago and Shur in this issue.

Do treated rectal tumors appear differently on MRI after chemotherapy versus chemoradiotherapy?

PURPOSE

Increasing studies have focused on neoadjuvant chemotherapy (NCT) in rectal cancer. However, few studies explored the differences in radiographic variation between patients treated with NCT and neoadjuvant chemoradiotherapy (NCRT).

METHODS

Stage II/III rectal cancer patients from March 2016 to December 2019 meeting the criteria treated with NCRT or NCT were included. MRI features, including tumor location, longitudinal length, DWI signal, MRI tumor regression grade (mrTRG), and radiomic texture features, before and after neoadjuvant treatments were reviewed.

RESULTS

116 patients with NCRT and 61 with NCT were analyzed. Among these patients, 46 patients in the NCRT group and 18 in the NCT group were responders with pathological TRG0-1. Within these responders, the mean tumor longitudinal length regression rate (TLRR) of the NCT group was 60.08 ± 11.17%, which was significantly higher than the 50.73 ± 15.28% of the NCRT group (p = 0.010). The proportion of high signal in the DWI image after NCT was higher than that of the NCRT group (88.89% vs 50.00%, p = 0.004). NCT responders had significantly higher median change rates than those of NCRT responders in 11 radiomic features, especially those shape features.

CONCLUSION

MRI images change differently between responders treated with NCRT and those with NCT in rectal cancer. The tumor volumetry and some radiomic features change more obviously in NCT responders, and the tumor signal changes more obviously in NCRT responders. During the evaluation of the response of the tumor to the neoadjuvant treatments, images of patients should be treated differently.

A primer on rectal MRI in patients on watch-and-wait treatment for rectal cancer

Total neoadjuvant treatment (TNT) for rectal cancer is becoming an accepted treatment paradigm and is changing the landscape of this disease, wherein up to 50% of patients who undergo TNT are able to avoid surgery. This places new demands on the radiologist in terms of interpreting degrees of response to treatment. This primer summarizes the Watch-and-Wait approach and the role of imaging, with illustrative "atlas-like" examples as an educational guide for radiologists. We present a brief literature summary of the evolution of rectal cancer treatment, with a focus on magnetic resonance imaging (MRI) assessment of response. We also discuss recommended guidelines and standards. We outline the common TNT approach entering mainstream practice. A heuristic and algorithmic approach to MRI interpretation is also offered. To illustrate management and common scenarios, we arranged the illustrative figures as follows: (I) Clinical complete response (cCR) achieved at the immediate post-TNT "decision point" scan time; (II) cCR achieved at some point during surveillance, later than the first post-TNT MRI; (III) near clinical complete response (nCR); (IV) incomplete clinical response (iCR); (V) discordant findings between MRI and endoscopy where MRI is falsely positive, even at follow-up; (VI) discordant cases where MRI seems to be falsely positive but is proven truly positive on follow-up endoscopy; (VII) cases where MRI is falsely negative; (VIII) regrowth of tumor in the primary tumor bed; (IX) regrowth outside the primary tumor bed; and (X) challenging scenarios, i.e., mucinous cases. This primer is offered to achieve its intended goal of educating radiologists on how to interpret MRI in patients with rectal cancer undergoing treatment using a TNT-type treatment paradigm and a Watch-and-Wait approach.

Time Interval Between the End of Neoadjuvant Therapy and Elective Resection of Locally Advanced Rectal Cancer in the CRONOS Study

Importance

The treatment for extraperitoneal locally advanced rectal cancer (LARC) is neoadjuvant therapy (NAT) followed by total mesorectal excision (TME). Robust evidence on the optimal time interval between NAT completion and surgery is lacking.

Objective

To assess the association of time interval between NAT completion and TME with short- and long-term outcomes. It was hypothesized that longer intervals increase the pathologic complete response (pCR) rate without increasing perioperative morbidity.

Design, Setting, and Participants

This cohort study included patients with LARC from 6 referral centers who completed NAT and underwent TME between January 2005 and December 2020. The cohort was divided into 3 groups depending on the time interval between NAT completion and surgery: short (≤8 weeks), intermediate (>8 and ≤12 weeks), and long (>12 weeks). The median follow-up duration was 33 months. Data analyses were conducted from May 1, 2021, to May 31, 2022. The inverse probability of treatment weighting method was used to homogenize the analysis groups.

Exposure

Long-course chemoradiotherapy or short-course radiotherapy with delayed surgery.

Main outcome and Measures

The primary outcome was pCR. Other histopathologic results, perioperative events, and survival outcomes constituted the secondary outcomes.

Results

Among the 1506 patients, 908 were male (60.3%), and the median (IQR) age was 68.8 (59.4-76.5) years. The short-, intermediate-, and long-interval groups included 511 patients (33.9%), 797 patients (52.9%), and 198 patients (13.1%), respectively. The overall pCR was 17.2% (259 of 1506 patients; 95% CI, 15.4%-19.2%). When compared with the intermediate-interval group, no association was observed between time intervals and pCR in short-interval (odds ratio [OR], 0.74; 95% CI, 0.55-1.01) and long-interval (OR, 1.07; 95% CI, 0.73-1.61) groups. The long-interval group was significantly associated with lower risk of bad response (tumor regression grade [TRG] 2-3; OR, 0.47; 95% CI, 0.24-0.91), systemic recurrence (hazard ratio, 0.59; 95% CI, 0.36-0.96), higher conversion risk (OR, 3.14; 95% CI, 1.62-6.07), minor postoperative complications (OR, 1.43; 95% CI, 1.04-1.97), and incomplete mesorectum (OR, 1.89; 95% CI, 1.02-3.50) when compared with the intermediate-interval group.

Conclusions and Relevance

Time intervals longer than 12 weeks were associated with improved TRG and systemic recurrence but may increase surgical complexity and minor morbidity.

Neoadjuvant chemotherapy induces an elevation of tumour apparent diffusion coefficient values in patients with ovarian cancer

OBJECTIVES

Multiparametric magnetic resonance imaging (mMRI) is the modality of choice in the imaging of ovarian cancer (OC). We aimed to investigate the feasibility of different types of regions of interest (ROIs) in the measurement of apparent diffusion coefficient (ADC) values of diffusion-weighted imaging in OC patients treated with neoadjuvant chemotherapy (NACT).

METHODS

We retrospectively enrolled 23 consecutive patients with advanced OC who had undergone NACT and mMRI. Seventeen of them had been imaged before and after NACT. Two observers independently measured the ADC values in both ovaries and in the metastatic mass by drawing on a single slice of (1) freehand large ROIs (L-ROIs) covering the solid parts of the whole tumour and (2) three small round ROIs (S-ROIs). The side of the primary ovarian tumour was defined. We evaluated the interobserver reproducibility and statistical significance of the change in tumoural pre- and post-NACT ADC values. Each patient's disease was defined as platinum-sensitive, semi-sensitive, or resistant. The patients were deemed either responders or non-responders.

RESULTS

The interobserver reproducibility of the L-ROI and S-ROI measurements ranged from good to excellent (ICC range: 0.71-0.99). The mean ADC values were significantly higher after NACT in the primary tumour (L-ROI p  < 0.001, S-ROIs p < 0.01), and the increase after NACT was associated with sensitivity to platinum-based chemotherapy. The changes in the ADC values of the omental mass were associated with a response to NACT.

CONCLUSION

The mean ADC values of the primary tumour increased significantly after NACT in the OC patients, and the amount of increase in omental mass was associated with the response to platinum-based NACT. Our study indicates that quantitative analysis of ADC values with a single slice and a whole tumour ROI placement is a reproducible method that has a potential role in the evaluation of NACT response in patients with OC.

TRIAL REGISTRATION

Retrospectively registered (institutional permission code: 5302501; date of the permission: 31.7.2020).

Predictive role of diffusion-weighted MRI in the assessment of response to total neoadjuvant therapy in locally advanced rectal cancer

OBJECTIVE

To investigate the predictive role of diffusion-weighted magnetic resonance imaging (DW-MRI) in the assessment of response to total neoadjuvant therapy (TNT) in patients with locally advanced rectal cancer (LARC).

METHODS

In this single-center retrospective study, patients with LARC who underwent staging MRI and TNT were enrolled. MRI-based staging, tumor volume, and DWI-ADC values were analyzed. Patients were classified as complete responders (pCR) and non-complete responders (non-pCR), according to post-surgical outcome. Pre-treatment ADC values were compared to pathological outcome, post-treatment downstaging, and reduction of tumor volume. The diagnostic accuracy of DWI-ADC in differentiating between pCR and non-pCR groups was calculated with receiver operating characteristic (ROC) analysis.

RESULTS

A total of 36 patients were evaluated (pCR, n = 20; non-pCR, n = 16). Pre-treatment ADC values were significantly different between the two groups (p = 0.034), while no association was found between pre-TNT tumor volume and pathological response. ADC values showed significant correlations with loco-regional downstaging after therapy (r = -0.537, p = 0.022), and with the reduction of tumor volume (r = -0.480, p = 0.044). ADC values were able to differentiate pCR from non-pCR patients with a sensitivity of 75% and specificity of 70%.

CONCLUSIONS

ADC values on pre-treatment MRI were strongly associated with the outcome in patients with LARC, both in terms of pathological response and in loco-regional downstaging after TNT, suggesting the use of DW-MRI as a potential predictive tool of response to therapy.

KEY POINTS

• ADC values of pre-TNT MRI examinations of patients with LARC were significantly associated with a pathological complete response (pCR) and with post-treatment regression of TNM staging. • An ADC value of 1.042 ×10^-3 mm²/s was found to be the optimal cutoff value for discriminating between pCR and non-pCR patients, with a sensitivity of 75% and specificity of 70%. • DW-MRI proved to have a potential predictive role in the assessment of response to therapy in patients with LARC, throughout the analysis of ADC map values.

Complete Response Evaluation of Locally Advanced Rectal Cancer to Neoadjuvant Chemoradiotherapy Using Textural Features Obtained from T2 Weighted Imaging and ADC Maps

BACKGROUND

The prediction of pathological responses for locally advanced rectal cancer using magnetic resonance imaging (MRI) after neoadjuvant chemoradiotherapy (CRT) is a challenging task for radiologists, as residual tumor cells can be mistaken for fibrosis. Texture analysis of MR images has been proposed to understand the underlying pathology.

OBJECTIVE

This study aimed to assess the responses of lesions to CRT in patients with locally advanced rectal cancer using the first-order textural features of MRI T2-weighted imaging (T2-WI) and apparent diffusion coefficient (ADC) maps.

METHODS

Forty-four patients with locally advanced rectal cancer (median age: 57 years) who underwent MRI before and after CRT were enrolled in this retrospective study. The first-order textural parameters of tumors on T2-WI and ADC maps were extracted. The textural features of lesions in pathologic complete responders were compared to partial responders using Student's t- or Mann-Whitney U tests. A comparison of textural features before and after CRT for each group was performed using the Wilcoxon rank sum test. Receiver operating characteristic curves were calculated to detect the diagnostic performance of the ADC.

RESULTS

Of the 44 patients evaluated, 22 (50%) were placed in a partial response group and 50% were placed in a complete response group. The ADC changes of the complete responders were statistically more significant than those of the partial responders (P = 0.002). Pathologic total response was predicted with an ADC cut-off of 1310 x 10-6 mm2/s, with a sensitivity of 72%, a specificity of 77%, and an accuracy of 78.1% after neoadjuvant CRT. The skewness of the T2-WI before and after neoadjuvant CRT showed a significant difference in the complete response group compared to the partial response group (P = 0.001 for complete responders vs. P = 0.482 for partial responders). Also, relative T2-WI signal intensity in the complete response group was statistically lower than that of the partial response group after neoadjuvant CRT (P = 0.006).

CONCLUSION

As a result of the conversion of tumor cells to fibrosis, the skewness of the T2-WI before and after neoadjuvant CRT was statistically different in the complete response group compared to the partial response group, and the complete response group showed statistically lower relative T2-WI signal intensity than the partial response group after neoadjuvant CRT. Additionally, the ADC cut-off value of 1310 × 10-6 mm2/s could be used as a marker for complete response along with absolute ADC value changes within this dataset.

Rectal cancer response to neoadjuvant chemoradiotherapy evaluated with MRI: Development and validation of a classification algorithm

OBJECTIVE

The aim of this study was to develop and validate a decision support model using data mining algorithms, based on morphologic features derived from MRI images, to discriminate between complete responders (CR) and non-complete responders (NCR) patients after neoadjuvant chemoradiotherapy (CRT), in a population of patients with locally advanced rectal cancer (LARC).

METHODS

Two populations were retrospectively enrolled: group A (65 patients) was used to train a data mining decision tree algorithm whereas group B (30 patients) was used to validate it. All patients underwent surgery; according to the histology evaluation, patients were divided in CR and NCR. Staging and restaging MRI examinations were retrospectively analysed and seven parameters were considered for data mining classification. Five different classification methods were tested and evaluated in terms of sensitivity, specificity, accuracy and AUC in order to identify the classification model able to achieve the best performance. The best classification algorithm was subsequently applied to group B for validation: sensitivity, specificity, positive and negative predictive value, accuracy and ROC curve were calculated. Inter and intra-reader agreement were calculated.

RESULTS

Four features were selected for the development of the classification algorithm: MRI tumor regression grade (MR-TRG), staging volume (SV), tumor volume reduction rate (TVRR) and signal intensity reduction rate (SIRR). The decision tree J48 showed the highest efficiency: when applied to group B, all the CR and 18/21 NCR were correctly classified (sensitivity 85.71%, specificity 100%, PPV 100%, NPV 94.2%, accuracy 95.7%, AUC 0.833). Both inter- and intra-reader evaluation showed good agreement (κ > 0.6).

CONCLUSIONS

The proposed decision support model may help in distinguishing between CR and NCR patients with LARC after CRT.

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.

Comparison of percentage changes in quantitative diffusion parameters for assessing pathological complete response to neoadjuvant therapy in locally advanced rectal cancer: a meta-analysis

PURPOSE

To evaluate and compare the diagnostic performance of percentage changes in apparent diffusion coefficient (∆ADC%) and slow diffusion coefficient (∆D%) for assessing pathological complete response (pCR) to neoadjuvant therapy in patients with locally advanced rectal cancer (LARC).

METHODS

A systematic search in PubMed, EMBASE, the Web of Science, and the Cochrane Library was performed to retrieve related original studies. For each parameter (∆ADC% and ∆D%), we pooled the sensitivity, specificity and calculated the area under summary receiver operating characteristic curve (AUROC) values. Meta-regression and subgroup analyses were performed to explore heterogeneity among the studies on ∆ADC%.

RESULTS

15 original studies (804 patients with 805 lesions, 15 studies on ∆ADC%, 4 of the studies both on ∆ADC% and ∆D%) were included. pCR was observed in 213 lesions (26.46%). For the assessment of pCR, the pooled sensitivity, specificity and AUROC of ∆ADC% were 0.83 (95% confidence intervals [CI] 0.76, 0.89), 0.74 (95% CI 0.66, 0.81), 0.87 (95% CI 0.83, 0.89), and ∆D% were 0.70 (95% CI 0.52, 0.84), 0.81 (95% CI 0.65, 0.90), 0.81 (95% CI 0.77, 0.84), respectively. In the four studies on the both metrics, ∆ADC% yielded an equivalent diagnostic performance (AUROC 0.80 [95% CI 0.76, 0.83]) to ∆D%, but lower than in the studies (n = 11) only on ∆ADC% (AUROC 0.88 [95% CI 0.85, 0.91]). Meta-regression and subgroup analyses showed no significant factors affecting heterogeneity.

CONCLUSIONS

Our meta-analysis confirms that ∆ADC% could reliably evaluate pCR in patients with LARC after neoadjuvant therapy. ∆D% may not be superior to ∆ADC%, which deserves further investigation.

Accuracy of MRI for nodal restaging in rectal cancer: a retrospective study of 166 cases

AIM

Assessing metastatic mesorectal nodal involvement is a challenge in rectal cancer, especially in the post chemoradiation setting. We aim to assess the accuracy of MRI for nodal restaging and the validity of SAR criteria (≥ 5 mm size being metastatic).

MATERIALS AND METHODS

This was an IRB-approved retrospective study of 166 patients with locally advanced rectal cancers, operated after neoadjuvant treatment. Two dedicated oncoradiologists reviewed the 166 post-chemoradiation presurgical MRIs in consensus. Nodal size and morphology (shape, margins, and signal intensity) were noted. The most accurate cut-off for size for predicting positive pN status was determined using the Youden index.

RESULTS

MRI understaged 30/166 (18%) and overstaged 40/166 (24%) patients using the SAR criteria. The most accurate cut-off for node size was 5.5 mm, with a sensitivity of 75%, specificity of 60.2%, PPV of 40.7%, NPV of 86.9% (95% CI:78-92.5%), accuracy of 64.2%, and area under the curve (AUC) 0.657 (95% CI-0.524-0.79). Morphological characteristics were not significant to determine involvement, with positive nodes including 42% of round and 31% of oval nodes, 40% of heterogeneous and 45% of homogeneous nodes, and 31% irregularly marginated and 46% nodes with regular margins being positive on pathology. MRI was accurate in predicting pathology for mucinous nodes in 9/29 (31%) cases. Seven cases which were yN2 on MRI and yN0 on pathology demonstrated mucinous changes on MRI and had acellular mucin on histopathology.

CONCLUSIONS

MRI has good negative predictive value, poor positive predictive value and moderate accuracy in nodal restaging. The cut-off of 5.5 mm demonstrated in our study is close to the SAR cut-off of 5 mm in the post-treatment setting. MRI accuracy is lower in patients with mucinous nodes.

Borderline Resectable and Locally Advanced Pancreatic Cancer: FDG PET/MRI and CT Tumor Metrics for Assessment of Pathologic Response to Neoadjuvant Therapy and Prediction of Survival

BACKGROUND. Imaging biomarkers of response to neoadjuvant therapy (NAT) for pancreatic ductal adenocarcinoma (PDA) are needed to optimize treatment decisions and long-term outcomes. OBJECTIVE. The purpose of this study was to investigate metrics from PET/MRI and CT to assess pathologic response of PDA to NAT and to predict overall survival (OS). METHODS. This retrospective study included 44 patients with ¹⁸F-FDG-avid borderline resectable or locally advanced PDA on pretreatment PET/MRI who also underwent post-NAT PET/MRI before surgery between August 2016 and February 2019. Carbohydrate antigen 19-9 (CA 19-9) level, metabolic metrics from PET/MRI, and morphologic metrics from CT (n = 34) were compared between pathologic responders (College of American Pathologists scores 0 and 1) and nonresponders (scores 2 and 3). AUCs were measured for metrics significantly associated with pathologic response. Relation to OS was evaluated with Cox proportional hazards models. RESULTS. Among 44 patients (22 men, 22 women; mean age, 62 ± 11.6 years), 19 (43%) were responders, and 25 (57%) were nonresponders. Median OS was 24 months (range, 6-42 months). Before treatment, responders and nonresponders did not differ in CA 19-9 level, metabolic metrics, or CT metrics (p > .05). After treatment, responders and nonresponders differed in complete metabolic response (CMR) (responders, 89% [17/19]; nonresponders, 40% [10/25]; p = .04], mean change in SUV_max (ΔSUV_max; responders, -70% ± 13%; nonresponders, -37% ± 42%; p < .001), mean change in SUV_max corrected to serum glucose level (ΔSUV_gluc) (responders, -74% ± 12%; nonresponders, -30% ± 58%; p < .001), RECIST response on CT (responders, 93% [13/14]; nonresponders, 50% [10/20]; p = .02)], and mean change in tumor volume on CT (ΔTvol) (responders, -85% ± 21%; nonresponders, 57% ± 400%; p < .001). The AUC of CMR for pathologic response was 0.75; ΔSUV_max, 0.83; ΔSUV_gluc, 0.87; RECIST, 0.71; and ΔTvol 0.86. The AUCs of bivariable PET/MRI and CT models were 0.83 (CMR and ΔSUV_max), 0.87 (CMR and ΔSUV_gluc), and 0.87 (RECIST and ΔTvol). OS was associated with CMR (p = .03), ΔSUV_max (p = .003), ΔSUV_gluc (p = .003), and RECIST (p = .046). CONCLUSION. Unlike CA 19-9 level, changes in metabolic metrics from PET/MRI and morphologic metrics from CT after NAT were associated with pathologic response and OS in patients with PDA, warranting prospective validation. CLINICAL IMPACT. Imaging metrics associated with pathologic response and OS in PDA could help guide clinical management and outcomes for patients with PDA who undergo emergency therapeutic interventions.

Prognostic implications of mucinous histology in stage III colon cancer with the receipt of adjuvant chemotherapy

Background

There is still a debate about the survival benefit of chemotherapy in stage III mucinous colon cancer, we then conduct a comprehensive assessment of the efficacy of adjuvant chemotherapy in this population.

Methods

The data used in the current study were extracted from the Surveillance, Epidemiology and End Results (SEER) database. Chi-squared (χ²) test was used to compared patient characteristics according to the histology. The outcome of the survival analysis used in the current study was cancer-specific survival (CSS). Univariable and multivariable analyses were carried out using the Cox proportional hazards regression models to evaluate the prognostic characteristics associated with CSS of colon cancer. And the risks of mortality were presented as hazard ratios (HRs) with 95% confidence intervals (CIs).

Results

A total of 68,976 patients diagnosed with stage III colon cancer were included in our analyses, including mucinous adenocarcinoma (MAC, N=6,592) and non-mucinous adenocarcinoma (NMA, N=62,384). In NMA, the receipt of chemotherapy had 46.0% independently decreased risk of colon cancer-specific mortality compared to non-chemotherapy group (HR =0.540, 95% CI: 0.523-0.558, P<0.001). In MAC, the receipt of chemotherapy had 37.7% independently decreased risk of colon cancer-specific mortality compared to non-chemotherapy group (HR =0.623, 95% CI: 0.566-0.685, P<0.001).

Conclusions

MAC was associated with worse prognosis and was less responsive to chemotherapy compared with NMA in stage III colon cancer. However, stage III mucinous colon cancer still need to be treated with chemotherapy because of the significant survival benefit and specialized treatment plans for MAC were quite necessary in the future.

MRI prediction of pathological response in locally advanced rectal cancer: when apparent diffusion coefficient radiomics meets conventional volumetry

AIM

To investigate the role of diffusion-weighted imaging (DWI), T2-weighted (W) imaging, and apparent diffusion coefficient (ADC) histogram analysis before, during, and after neoadjuvant chemoradiotherapy (CRT) in the prediction of pathological response in patients with locally advanced rectal cancer (LARC).

MATERIALS AND METHODS

Magnetic resonance imaging (MRI) at 1.5 T was performed in 43 patients with LARC before, during, and after CRT. Tumour volume was measured on both T2-weighted (V_T2W) and on DWI at b=1,000 images (V_b,1,000) at each time point, hence the tumour volume reduction rate (ΔV_T2W and ΔV_b,1,000) was calculated. Whole-lesion (three-dimensional [3D]) first-order texture analysis of the ADC map was performed. Imaging parameters were compared to the pathological tumour regression grade (TRG). The diagnostic performance of each parameter in the identification of complete responders (CR; TRG4), partial responders (PR; TRG3) and non-responders (NR; TRG0-2) was evaluated by multinomial regression analysis and receiver operating characteristics curves.

RESULTS

After surgery, 11 patients were CR, 22 PR, and 10 NR. Before CRT, predictions of CR resulted in an ADC value of the 75th percentile and median, with good accuracy (74% and 86%, respectively) and sensitivity (73% and 82%, respectively). During CRT, the best predictor of CR was ΔV_T2W (-58.3%) with good accuracy (81%) and excellent sensitivity (91%). After CRT, the best predictors of CR were ΔV_T2W (-82.8%) and ΔV_{b, 1,000} (-86.8%), with 84% accuracy in both cases and 82% and 91% sensitivity, respectively.

CONCLUSIONS

The median ADC value at pre-treatment MRI and ΔV_T2W (from pre-to-during CRT MRI) may have a role in early and accurate prediction of response to treatment. Both ΔV_T2W and ΔV_b,1,000 (from pre-to-post CRT) can help in the identification of CR after CRT.

Diffusion weighted imaging improves diagnostic ability of MRI for determining complete response to neoadjuvant therapy in locally advanced rectal cancer

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The rate of pathological complete response (pCR) following NACRT was 14.7 %.

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Combination of morphology and DWI patterns was 89–96 % accurate in predicting pCR.

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Radiologists of varying experience agreed best with combined approach.

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Radiologists were more confident of their response using the combined approach.

Purpose

To assess the diagnostic performance, interobserver agreement and confidence level for determining response to neoadjuvant chemoradiotherapy (NACRT) using morphology based MR-tumour regression grade (MR TRG), diffusion weighted imaging (DWI) patterns and their combination in patients with locally advanced rectal cancer.

Methods

This was a retrospective study including patients with locally advanced rectal cancer treated with NACRT and subsequent surgery. Two independent radiologists blinded to the histopathology reviewed staging and restaging MRI. Diagnostic performance of morphology based MR-TRG, DWI patterns and their combination for determining complete (CR) and incomplete (IR) response was assessed with pathological response as the reference. Likert’s scale was used to assess the radiologist’s level of confidence. Interobserver agreement was determined using Kappa statistics.

Results

The study included 251 patients (mean age of 47.9+/-14 (range 19–86) years, M:F = 164:87). Rate of pathological CR was 14.7 % (n = 37). Pattern based interpretation of DWI and combined approach (DWI + T2-HR) had superior diagnostic performance than morphology based assessment alone with area under curve (AUC) for T2HR, DWI and their combination being 0.531, 0.887, 0.874 respectively for observer 1 and 0.558, 0.653, 0.678 respectively for observer 2, p < 0.001. Interobserver agreement was substantial (k = 0.688) for combined approach, moderate (k = 0.402) for DWI patterns and fair (k = 0.265) for T2 HR MRI with both observers exhibiting highest level of confidence for determining response with the combined approach.

Conclusion

Complete response to neoadjuvant chemoradiotherapy can be determined with excellent accuracy, substantial interobserver agreement and high level of confidence by combined interpretation of DWI and T2 high resolution MRI.

Diagnostic accuracy of b800 and b1500 DWI-MRI of the pelvis to detect residual rectal adenocarcinoma: a multi-reader study

PURPOSE

To compare the sensitivity, specificity and intra-observer and inter-observer agreement of pelvic magnetic resonance imaging (MRI) b800 and b1500 s/mm² sequences in the detection of residual adenocarcinoma after neoadjuvant chemoradiation (CRT) for locally advanced rectal cancer (LARC).

INTRODUCTION

Detection of residual adenocarcinoma after neoadjuvant CRT for LARC has become increasingly important and relies on both MRI and endoscopic surveillance. Optimal MRI diffusion b values have yet to be established for this clinical purpose.

METHODS

From our MRI database between 2018 and 2019, we identified a cohort of 28 patients after exclusions who underwent MRI of the rectum before and after neoadjuvant chemoradiation with a protocol that included both b800 and b1500 s/mm² diffusion sequences. Four radiologists experienced in rectal MRI interpreted the post-CRT MRI studies with either b800 DWI or b1500 DWI, and a minimum of 2 weeks later re-interpreted the same studies using the other b value sequence. Surgical pathology or endoscopic follow-up for 1 year without tumor re-growth was used as the reference standard. Descriptive statistics compared accuracy for each reader and for all readers combined between b values. Inter-observer agreement was assessed using kappa statistics. A p value of 0.05 or less was considered significant.

RESULTS

Within the cohort, 19/28 (67.9%) had residual tumor, while 9/28 (32.1%) had a complete response. Among four readers, one reader had increased sensitivity for detection of residual tumor at b1500 s/mm² (0.737 vs. 0.526, p = 0.046). There was no significant difference between detection of residual tumor at b800 and at b1500 for the rest of the readers. With all readers combined, the pooled sensitivity was 0.724 at b1500 versus 0.605 at b800, but this was not significant (p = 0.119). There was no difference in agreement between readers at the two b value settings (67.8% at b800 vs. 72.0% at b1500), or for any combination of individual readers.

CONCLUSION

Aside from one reader demonstrating increased sensitivity, no significant difference in accuracy parameters or inter-observer agreement was found between MR using b800 and b1500 for the detection of residual tumor after neoadjuvant CRT for LARC. However, there was a suggestion of a trend towards increased sensitivity with b1500, and further studies using larger cohorts may be needed to further investigate this topic.

Diagnostic accuracy of b800 and b1500 DWI-MRI of the pelvis to detect residual rectal adenocarcinoma: a multi-reader study

PURPOSE

To compare the sensitivity, specificity and intra-observer and inter-observer agreement of pelvic magnetic resonance imaging (MRI) b800 and b1500 s/mm² sequences in the detection of residual adenocarcinoma after neoadjuvant chemoradiation (CRT) for locally advanced rectal cancer (LARC).

INTRODUCTION

Detection of residual adenocarcinoma after neoadjuvant CRT for LARC has become increasingly important and relies on both MRI and endoscopic surveillance. Optimal MRI diffusion b values have yet to be established for this clinical purpose.

METHODS

From our MRI database between 2018 and 2019, we identified a cohort of 28 patients after exclusions who underwent MRI of the rectum before and after neoadjuvant chemoradiation with a protocol that included both b800 and b1500 s/mm² diffusion sequences. Four radiologists experienced in rectal MRI interpreted the post-CRT MRI studies with either b800 DWI or b1500 DWI, and a minimum of 2 weeks later re-interpreted the same studies using the other b value sequence. Surgical pathology or endoscopic follow-up for 1 year without tumor re-growth was used as the reference standard. Descriptive statistics compared accuracy for each reader and for all readers combined between b values. Inter-observer agreement was assessed using kappa statistics. A p value of 0.05 or less was considered significant.

RESULTS

Within the cohort, 19/28 (67.9%) had residual tumor, while 9/28 (32.1%) had a complete response. Among four readers, one reader had increased sensitivity for detection of residual tumor at b1500 s/mm² (0.737 vs. 0.526, p = 0.046). There was no significant difference between detection of residual tumor at b800 and at b1500 for the rest of the readers. With all readers combined, the pooled sensitivity was 0.724 at b1500 versus 0.605 at b800, but this was not significant (p = 0.119). There was no difference in agreement between readers at the two b value settings (67.8% at b800 vs. 72.0% at b1500), or for any combination of individual readers.

CONCLUSION

Aside from one reader demonstrating increased sensitivity, no significant difference in accuracy parameters or inter-observer agreement was found between MR using b800 and b1500 for the detection of residual tumor after neoadjuvant CRT for LARC. However, there was a suggestion of a trend towards increased sensitivity with b1500, and further studies using larger cohorts may be needed to further investigate this topic.