Pre-operative staging of rectal cancer: a review of imaging techniques

Oncological outcomes of local excision versus radical surgery for early rectal cancer in the context of staging and surveillance: A systematic review and meta-analysis

BACKGROUND

Local resection (LR) methods for rectal cancer are generally considered in the palliative setting or for patients deemed a high anaesthetic risk. This systematic review and meta-analysis aimed to compare oncological outcomes of LR and radical resection (RR) for early rectal cancer in the context of staging and surveillance assessment.

METHODS

A literature search of MEDLINE, Embase and Emcare databases was performed for studies that reported data on clinical outcomes for both LR and RR for early rectal cancer from January 1995 to April 2023. Meta-analysis was performed using random-effect models and between-study heterogeneity was assessed. The quality of assessment was assessed using the Newcastle-Ottawa Scale for observational studies and the Cochrane Risk of Bias 2.0 tool for randomised controlled trials.

RESULTS

Twenty studies with 12,022 patients were included: 6,476 patients had LR and 5,546 patients underwent RR. RR led to an improvement in 5-year overall survival (OR 1.84; 95 % CI 1.54-2.20; p < 0.0001; I2 20 %) and local recurrence (OR 3.06; 95 % CI 2.02-4.64; p < 0.0001; I2 39 %) when compared to LR. However, when staging and surveillance methods were clearly adopted in LR cases, there was an improvement in R0 rates (96.7 % vs 85.6 %), 5-year disease-free survival (93.0 % vs 77.9 %) and overall survival (81.6 % vs 79.0 %) compared to when staging and surveillance was not reported/performed.

CONCLUSIONS

LR may be appropriate for selected patients without poor prognostic factors in early rectal cancer. This study also highlights that there is currently no single standardised staging or surveillance approach being adopted in the management of early rectal cancer. A more specified and standardised preoperative staging for patient selection as well as clinical and image-based surveillance protocols is needed.

Pretreatment MRI-detected extramural venous invasion as a prognostic and predictive biomarker for neoadjuvant chemoradiotherapy in non-metastatic rectal cancer: a propensity score matched analysis

OBJECTIVES

This study evaluated pretreatment magnetic resonance imaging (MRI)-detected extramural venous invasion (pmrEMVI) as a predictor of survival after neoadjuvant chemoradiotherapy (nCRT) in patients with locally advanced rectal cancer (LARC).

MATERIALS AND METHODS

Medical records of 1184 patients with rectal adenocarcinoma who underwent TME between January 2011 and December 2016 were reviewed. MRI data were collected from a computerized radiologic database. Cox proportional hazards analysis was used to assess local, systemic recurrence, and disease-free survival risk based on pretreatment MRI-assessed tumor characteristics. After propensity score matching (PSM) for pretreatment MRI features, nCRT therapeutic outcomes according to pmrEMVI status were evaluated. Cox proportional hazards analysis was used to identify risk factors for early recurrence in patients receiving nCRT.

RESULTS

Median follow-up was 62.8 months. Among all patients, the presence of pmrEMVI was significantly associated with worse disease-free survival (DFS; HR 1.827, 95% CI 1.285-2.597, p = 0.001) and systemic recurrence (HR 2.080, 95% CI 1.400-3.090, p < 0.001) but not local recurrence. Among patients with pmrEMVI, nCRT provided no benefit for oncological outcomes before or after PSM. Furthermore, pmrEMVI( +) was the only factor associated with early recurrence on multivariate analysis in patients receiving nCRT.

CONCLUSIONS

pmrEMVI is a poor prognostic factor for DFS and SR in patients with non-metastatic rectal cancer and also serves as a predictive biomarker of poor DFS and SR following nCRT in LARC. Therefore, for patients who are positive for pmrEMVI, consideration of alternative treatment strategies may be warranted.

CLINICAL RELEVANCE STATEMENT

This study demonstrated the usefulness of pmrEMVI as a predictive biomarker for nCRT, which may assist in initial treatment decision-making in patients with non-metastatic rectal cancer.

KEY POINTS

• Pretreatment MRI-detected extramural venous invasion (pmrEMVI) was significantly associated with worse disease-free survival and systemic recurrence in patients with non-metastatic rectal cancer. • pmrEMVI is a predictive biomarker of poor DFS following nCRT in patients with LARC. • The presence of pmrEMVI was the only factor associated with early recurrence on multivariate analysis in patients receiving nCRT.

Prognostic value of multi b-value DWI in patients with locally advanced rectal cancer

OBJECTIVES

To evaluate the potential of multi b-value DWI in predicting the prognosis of patients with locally advanced rectal cancer (LARC).

METHODS

From 2015 to 2019, a total of 161 patients with LARC were enrolled and randomly sampled into a training set (n = 113) and validation set (n = 48). Multi b-value DWI (b = 0~1500 s/mm²) scans were postprocessed to generate functional parameters, including apparent diffusion coefficient (ADC), Dt, Dp, f, distributed diffusion coefficient (DDC), and α. Histogram features of each functional parameter were submitted into Least absolute shrinkage and selection operator (LASSO) and stepwise multivariate COX analysis to generate DWI_score based on the training set. The prognostic model was constructed with functional parameter, DWI_score, and clinicopathologic factors by using univariate and multivariate COX analysis on the training set and verified on the validation set.

RESULTS

Multivariate COX analysis revealed that DWI_score was an independent indicator for 5-year progression-free survival (PFS, HR = 5.573, p < 0.001), but not for overall survival (OS, HR = 2.177, p = 0.051). No mean value of functional parameters was correlated with PFS or OS. Prognostic model for 5-year PFS based on DWI_score, TNM-stage, mesorectal fascia (MRF), and extramural venous invasion (EMVI) showed good performance both in the training set (AUC = 0.819) and validation set (AUC = 0.815).

CONCLUSIONS

The DWI_score based on histogram features of multi b-value DWI functional parameters was an independent factor for PFS of LARC and the prognostic model with a combination of DWI_score and clinicopathologic factors could indicate the progression risk before treatment.

KEY POINTS

• Mean value of functional parameters obtained from multi b-value DWI might not be useful to assess the prognosis of LARC. • The DWI_score based on histogram features of multi b-value DWI functional parameters was an independent prognosis factor for PFS of LARC. • Prognostic model based on DWI_score and clinicopathologic factors could indicate the progression risk of LARC before treatment.

How We Treat Localized Rectal Cancer-An Institutional Paradigm for Total Neoadjuvant Therapy

Total neoadjuvant therapy (TNT)-the neoadjuvant employment of radiotherapy (RT) or chemoradiation (CRT) as well as chemotherapy (CHT) before surgery-may lead to increased pathological complete response (pCR) rates as well as a reduction in the risk of distant metastases in locally advanced rectal cancer. Furthermore, increased response rates may allow organ-sparing strategies in a growing number of patients with low rectal cancer and upfront immunotherapy has shown very promising early results in patients with microsatellite instability (MSI)-high/mismatch-repair-deficient (dMMR) tumors. Despite the lack of a generally accepted treatment standard, we strongly believe that existing data is sufficient to adopt the concept of TNT and immunotherapy in clinical practice. The treatment algorithm presented in the following is based on our interpretation of the current data and should serve as a practical guide for treating physicians-without any claim to general validity.

Multimodal Treatment of Rectal Cancer

BACKGROUND

Colorectal cancer is one of the three most common types of cancer in Germany. Approximately 30% of these cancers are located in the rectum, corresponding to about 18 000 new cases per year.

METHODS

This review is based on publications retrieved by a selective search in the PubMed database, including current guidelines and recommendations.

RESULTS

Specialized imaging, particularly magnetic resonance imaging, is essential for treatment planning. In very early stages of this disease, tumors without risk factors can be excised locally. Otherwise, radical surgical resection with lymphadenectomy remains the standard treatment, and can be performed either minimally invasive or open. At present, neoadjuvant treatment plans are evolving in the direction of total neoadjuvant therapy. In addition, recent studies investigate whether the improved efficacy of neoadjuvant therapy might now enable patients with a complete clinical remission to be spared from surgical resection (organ-preserving watch-and-wait strategy).

CONCLUSION

The treatment of rectal cancer is a prime example of an interdisciplinary, multimodal approach. In the past, the focus was mainly on improving oncologic outcomes; at present, increasing attention is being devoted to the patients' quality of life as well and the functional aspects of the various modes of treatment.

MRI of rectal cancer-relevant anatomy and staging key points

Rectal cancer has the eighth highest cancer incidence worldwide, and it is increasing in young individuals. However, in countries with a high human development index, mortality is decreasing, which may reflect better patient management, imaging being key. We rely on imaging to establish the great majority of clinical tumour features for therapeutic decision-making, namely tumour location, depth of invasion, lymph node involvement, circumferential resection margin status and extramural venous invasion. Despite major improvements in technique resulting in better image quality, and notwithstanding the dissemination of guidelines and examples of standardised reports, rectal cancer staging is still challenging on the day-to-day practice, and we believe there are three reasons. First, the normal posterior pelvic compartment anatomy and variants are not common knowledge to radiologists; second, not all rectal cancers fit in review paper models, namely the very early, the very low and the mucinous; and third, the key clinical tumour features may be tricky to analyse. In this review, we discuss the normal anatomy of the rectum and posterior compartment of the pelvis, systematise all rectal cancer staging key points and elaborate on the particularities of early, low and mucinous tumours. We also include our suggested reporting templates and a discussion of its comparison to the reporting templates provided by ESGAR and SAR.

Application value of biplane transrectal ultrasonography plus ultrasonic elastosonography and contrast-enhanced ultrasonography in preoperative T staging after neoadjuvant chemoradiotherapy for rectal cancer

PURPOSE

To determine the accuracy of biplane transrectal ultrasonography (TRUS) plus ultrasonic elastosonography (UE) and contrast-enhanced ultrasonography (CEUS) in preoperative T staging after neoadjuvant chemoradiotherapy for rectal cancer.

MATERIALS AND METHODS

Fifty-three patients with advanced lower rectal cancer were examined before and after neoadjuvant chemoradiotherapy with use of TRUS plus UE and CEUS and were diagnosed as having T stage disease. We compared ultrasonic T stages before and after neoadjuvant chemoradiotherapy and analyzed any changes. Also, with postoperative pathological stages as the gold standard, we compared ultrasonic and pathological T stages and determined their consistency by the kappa statistic.

RESULTS

For patients with rectal cancer, ultrasonic T stages were lower after neoadjuvant chemoradiotherapy than before, with a statistically significant difference (P < 0.05). The posttreatment downstaging rate was 39.6% (21/53). A total of 84.9% received correct staging with use of biplane TRUS plus UE and CEUS in the evaluation of preoperative T staging after neoadjuvant chemoradiotherapy for rectal cancer, which was highly consistent with that of pathological staging (κ = 0.768, P < 0.05). Its sensitivities were 80.0%, 50.0%, 75.0%, 96.3%, and 100% in the diagnoses of stages T0 to T4 rectal cancers, respectively; the specificities were 95.4%, 97.9%, 95.1%, 88.5%, and 100% at stages T0 to T4, respectively.

CONCLUSION

Biplane TRUS plus UE and CEUS can be used to accurately perform preoperative T staging in rectal cancer after neoadjuvant chemoradiotherapy; in addition, this procedure well reflects changes in depth of rectal cancer invasion into the intestinal wall before and after neoadjuvant chemoradiotherapy. It is of great value in clinically evaluating the efficacy of neoadjuvant chemoradiotherapy, in selecting therapeutic regimens, and in avoiding overtreatment.

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.

Endoscopic ultrasonography and computed tomography scanning for preoperative staging of colonic cancer

PURPOSE

With an increasing demand for more accurate preoperative staging methods for colon cancer, we aimed to compare preoperative tumour (T)- and nodal (N)-stage in patients with left-sided colon cancer by endoscopic ultrasonography (EUS) and computed tomography (CT) with post-operative histology as gold standard.

METHODS

A total of 44 patients were prospectively recruited at Herlev and Roskilde University Hospitals during November 2014-January 2016. Thirty-five patients were included in the final analysis and underwent EUS, CT and surgery within 2 weeks. Diagnostic values were evaluated for "low risk" (T1+T2+T3 with ≤5 mm extramural invasion) and "high risk" (T3 with >5 mm of extramural spread + T4) colonic cancer.

RESULTS

Sensitivity and specificity in "low risk" colonic cancer evaluated with EUS was 0.90 [0.74;0.98] and 0.75 [0.19;0.99] and with CT 0.96 [0.80;0.99] and 0.25 [<0.01;0.81]. EUS and CT were poor in predicting N0 or N+ disease.

CONCLUSIONS

The sensitivity of EUS and CT were good and comparable regarding T-stage evaluation, while EUS had a significantly higher specificity in the evaluation of "low risk" tumours. The results obtained for "high risk" colonic cancer were difficult to evaluate due to small patient numbers. EUS could be considered as a supplement to CT scans in selecting patients for neoadjuvant therapies, or local transmural treatment, in the future.

TRIAL REGISTRATION

NCT02324023.

Addressing unwarranted variations in colorectal cancer outcomes: a conceptual approach

In the clinical setting, the term 'unwarranted variation' refers to variations in patient outcomes that cannot be explained by the patient's underlying illness or medical needs, or the dictates of evidence-based medicine. These types of variations persist even after adjusting for patient-specific factors. Unwarranted variation depends on a complex mix of disparities, including inequalities in access to appropriate care in a wide variety of geographical and cultural settings, in the uptake and application of clinical knowledge, in the prioritization and allocation of resources, and differences in organizational and professional culture. Nevertheless, unwarranted variation has been inexorably linked with clinical practice. Thus, awareness of the antecedents of unwarranted variations in clinical practice is strategically important. In this Perspective, we discuss these antecedents in colorectal cancer clinical care pathways with an emphasis upon the multidisciplinary team (MDT), and suggest pragmatic steps that could be taken to address latent unwarranted variation.