Locally recurrent rectal cancer: what the radiologist should know

Dutch national guidelines for locally recurrent rectal cancer

Due to improvements in treatment for primary rectal cancer, the incidence of LRRC has decreased. However, 6-12% of patients will still develop a local recurrence. Treatment of patients with LRRC can be challenging, because of complex and heterogeneous disease presentation and scarce - often low-grade - data steering clinical decisions. Previous consensus guidelines have provided some direction regarding diagnosis and treatment, but no comprehensive guidelines encompassing all aspects of the clinical management of patients with LRRC are available to date. The treatment of LRRC requires a multidisciplinary approach and overarching expertise in all domains. This broad expertise is often limited to specific expert centres, with dedicated multidisciplinary teams treating LRRC. A comprehensive, narrative literature review was performed and used to develop the Dutch National Guideline for management of LRRC, in an attempt to guide decision making for clinicians, regarding the complete clinical pathway from diagnosis to surgery.

Local Recurrences in Rectal Cancer: MRI vs. CT

Rectal cancers are often considered a distinct disease from colon cancers as their survival and management are different. Particularly, the risk for local recurrence (LR) is greater than in colon cancer. There are many factors predisposing to LR such as postoperative histopathological features or the mesorectal plane of surgical resection. In addition, the pattern of LR in rectal cancer has a prognostic significance and an important role in the choice of operative approach and. Therefore, an optimal follow up based on imaging is critical in rectal cancer. The aim of this review is to analyse the risk and the pattern of local recurrences in rectal cancer and to provide an overview of the role of imaging in early detection of LRs. We performed a literature review of studies published on Web of Science and MEDLINE up to January 2023. We also reviewed the current guidelines of National Comprehensive Cancer Network (NCCN) and the European Society for Medical Oncology (ESMO). Although the timing and the modality of follow-up is not yet established, the guidelines usually recommend a time frame of 5 years post surgical resection of the rectum. Computed Tomography (CT) scans and/or Magnetic Resonance Imaging (MRI) are the main imaging techniques recommended in the follow-up of these patients. PET-CT is not recommended by guidelines during post-operative surveillance and it is generally used for problem solving.

Radiomic Features from Post-Operative (18)F-FDG PET/CT and CT Imaging Associated with Locally Recurrent Rectal Cancer: Preliminary Findings

Locally Recurrent Rectal Cancer (LRRC) remains a major clinical concern; it rapidly invades pelvic organs and nerve roots, causing severe symptoms. Curative-intent salvage therapy offers the only potential for cure but it has a higher chance of success when LRRC is diagnosed at an early stage. Imaging diagnosis of LRRC is very challenging due to fibrosis and inflammatory pelvic tissue, which can mislead even the most expert reader. This study exploited a radiomic analysis to enrich, through quantitative features, the characterization of tissue properties, thus favoring an accurate detection of LRRC by Computed Tomography (CT) and 18F-FDG-Positron Emission Tomography/CT (PET/CT). Of 563 eligible patients undergoing radical resection (R0) of primary RC, 57 patients with suspected LRRC were included, 33 of which were histologically confirmed. After manually segmenting suspected LRRC in CT and PET/CT, 144 Radiomic Features (RFs) were generated, and RFs were investigated for univariate significant discriminations (Wilcoxon rank-sum test, p < 0.050) of LRRC from NO LRRC. Five RFs in PET/CT (p < 0.017) and two in CT (p < 0.022) enabled, individually, a clear distinction of the groups, and one RF was shared by PET/CT and CT. As well as confirming the potential role of radiomics to advance LRRC diagnosis, the aforementioned shared RF describes LRRC as tissues having high local inhomogeneity due to the evolving tissue's properties.

Post-Surgical Imaging Assessment in Rectal Cancer: Normal Findings and Complications

Rectal cancer (RC) is one of the deadliest malignancies worldwide. Surgery is the most common treatment for RC, performed in 63.2% of patients. The type of surgical approach chosen aims to achieve maximum residual function with the lowest risk of recurrence. The selection is made by a multidisciplinary team that assesses the characteristics of the patient and the tumor. Total mesorectal excision (TME), including both low anterior resection (LAR) and abdominoperineal resection (APR), is still the standard of care for RC. Radical surgery is burdened by a 31% rate of major complications (Clavien-Dindo grade 3-4), such as anastomotic leaks and a risk of a permanent stoma. In recent years, less-invasive techniques, such as local excision, have been tested. These additional procedures could mitigate the morbidity of rectal resection, while providing acceptable oncologic results. The "watch and wait" approach is not a globally accepted model of care but encouraging results on selected groups of patients make it a promising strategy. In this plethora of treatments, the radiologist is called upon to distinguish a physiological from a pathological postoperative finding. The aim of this narrative review is to identify the main post-surgical complications and the most effective imaging techniques.

Development of a consensus-based delineation guideline for locally recurrent rectal cancer

BACKGROUND AND PURPOSE

Neoadjuvant chemoradiotherapy (nCRT) is used in locally recurrent rectal cancer (LRRC) to increase chances of a radical surgical resection. Delineation in LRRC is hampered by complex disease presentation and limited clinical exposure. Within the PelvEx II trial, evaluating the benefit of chemotherapy preceding nCRT for LRRC, a delineation guideline was developed by an expert LRRC team.

MATERIALS AND METHODS

Eight radiation oncologists, from Dutch and Swedish expert centres, participated in two meetings, delineating GTV and CTV in six cases. Regions at-risk for re-recurrence or irradical resection were identified by eleven expert surgeons and one expert radiologist. Target volumes were evaluated multidisciplinary. Inter-observer variation was analysed.

RESULTS

Inter-observer variation in delineation of LRRC appeared large. Multidisciplinary evaluation per case is beneficial in determining target volumes. The following consensus regarding target volumes was reached. GTV should encompass all tumour, including extension into OAR if applicable. If the tumour is in fibrosis, GTV should encompass the entire fibrotic area. Only if tumour can clearly be distinguished from fibrosis, GTV may be reduced, as long as the entire fibrotic area is covered by the CTV. CTV is GTV with a 1 cm margin and should encompass all at-risk regions for irradical resection or re-recurrence. CTV should not be adjusted towards other organs. Multifocal recurrences should be encompassed in one CTV. Elective nodal delineation is only advised in radiotherapy-naïve patients.

CONCLUSION

This study provides a first consensus-based delineation guideline for LRRC. Analyses of re-recurrences is needed to understand disease behaviour and to optimize delineation guidelines accordingly.

Review of Radiomics- and Dosiomics-based Predicting Models for Rectal Cancer

By breaking the traditional medical image analysis framework, precision medicine–radiomics has attracted much attention in the past decade. The use of various mathematical algorithms offers radiomics the ability to extract vast amounts of detailed features from medical images for quantitative analysis and analyzes the confidential information related to the tumor in the image, which can establish valuable disease diagnosis and prognosis models to support personalized clinical decisions. This article summarizes the application of radiomics and dosiomics in radiation oncology. We focus on the application of radiomics in locally advanced rectal cancer and also summarize the latest research progress of dosiomics in radiation tumors to provide ideas for the treatment of future related diseases, especially ¹²⁵I CT-guided radioactive seed implant brachytherapy.

Added value of quantitative, multiparametric 18F-FDG PET/MRI in the locoregional staging of rectal cancer

PURPOSE

The purpose of this study was to determine whether multiparametric positron emission tomography/magnetic resonance imaging (mpPET/MRI) can improve locoregional staging of rectal cancer (RC) and to assess its prognostic value after resection.

METHODS

In this retrospective study, 46 patients with primary RC, who underwent multiparametric 18F-fluorodeoxyglucose (FDG) PET/MRI, followed by surgical resection without chemoradiotherapy, were included. Two readers reviewed T- and N- stage, mesorectal involvement, sphincter infiltration, tumor length, and distance from anal verge. In addition, diffusion-weighted imaging (DWI) and PET parameters were extracted from the multiparametric protocol and were compared to radiological staging as well as to the histopathological reference standard. Clinical and imaging follow-up was systematically assessed for tumor recurrence and death.

RESULTS

Locally advanced rectal cancers (LARC) exhibited significantly higher metabolic tumor volume (MTV, AUC 0.74 [95% CI 0.59-0.89], p = 0.004) and total lesion glycolysis (TLG, AUC 0.70 [95% CI 0.53-0.87], p = 0.022) compared to early tumors. T-stage was associated with MTV (AUC 0.70 [95% CI 0.54-0.85], p = 0.021), while N-stage was better assessed using anatomical MRI sequences (AUC 0.72 [95% CI 0.539-0.894], p = 0.032). In the multivariate regression analysis, depending on the model, both anatomical MRI sequences and MTV/TLG were capable of detecting LARC. Combining anatomical MRI stage and MTV/TLG led to a superior diagnostic performance for detecting LARC (AUC 0.81, [95% CI 0.68-0.94], p &lt; 0.001). In the survival analysis, MTV was independently associated with overall survival (HR 1.05 [95% CI 1.01-1.10], p = 0.044).

CONCLUSION

Multiparametric PET-MRI can improve identification of locally advanced tumors and, hence, help in treatment stratification. It provides additional information on RC tumor biology and may have prognostic value.

Efficacy of endoscopic surveillance in the detection of local recurrence after radical rectal cancer surgery is limited? A retrospective study

Background

Rectal cancer, one of most common neoplasms, is characterized by an overall survival rate exceeding 60%. Nonetheless, local recurrence (LR) following surgery for rectal cancer remains a formidable clinical problem. The aim of this study was to assess the value of postoperative endoscopic surveillance (PES) for the early detection of LR in rectal cancer after radical anterior resection with sigmoid-rectal anastomosis.

Methods

We performed an anterior resection in 228 patients with stages I‑III rectal cancer who had undergone surgery from 2001 to 2008 in the Oncology Center in Bydgoszcz, Poland. Of these patients, 169 had perioperative radiotherapy or radiochemotherapy. All patients underwent PES with abdominal and pelvic imaging (abdominal ultrasound, computed tomography, magnetic resonance) and clinical examination. Sensitivities, specificities, positive likelihood ratios, negative likelihood ratios, and receiver operating characteristic curves were calculated to compare the value of colonoscopy versus imaging techniques for the diagnosis of LR.

Results

During the 5-year follow-up, recurrences occurred in 49 (21%) patients; of these, 15 (6%) had LR, which was most often located outside the intestinal lumen (n = 10, 4%). Anastomotic LR occurred in 5 (2%) patients. The mean time to anastomotic LR was 30 months after initial surgery, similar to that of other locations (29 months). Both imaging and endoscopy were shown to be efficient techniques for the diagnosis of LR in anastomotic sites. In the study group, endoscopy did not provide any additional benefit in patients who were receiving radiation therapy.

Conclusions

The benefit of PES for the detection of LR after curative treatment of rectal cancer is limited and not superior to imaging techniques. It remains a useful method, however, for the histopathological confirmation of suspected or confirmed recurrence.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12957-021-02413-0.

A phase III randomized trial evaluating chemotherapy followed by pelvic reirradiation versus chemotherapy alone as preoperative treatment for locally recurrent rectal cancer - GRECCAR 15 trial protocol

AIM

Treatment strategies in locally recurrent rectal cancer (LRRC) are complex and need to be balanced against previous treatments received for the primary rectal cancer. Radiotherapy is an important component of treatment in LRRC. However, there is little high-quality evidence on the role of reirradiation in this cohort. Therefore, the aim of this trial is to assess the efficacy of neoadjuvant chemotherapy followed by pelvic reirradiation versus neoadjuvant chemotherapy alone on the rate of curative surgery (R0) in previously irradiated patients with LRRC.

METHOD

GRECCAR 15 is a prospective, multicentre, open-label, outcome assessor-blinded, superiority randomized controlled phase III clinical trial comparing neoadjuvant chemotherapy followed by pelvic reirradiation versus neoadjuvant chemotherapy alone in patients with LRRC previously irradiated for the primary cancer. Adult patients (>18 years old) with a histologically proven resectable LRRC, who have previously received pelvic radiotherapy for their primary rectal cancer at a dose of 25-50.4 Gy, and an Eastern Cooperative Oncology Group performance status of <2 will be eligible to participate. The pelvic reirradiation will consist of conformational intensity-modulated external irradiation, delivering a dose of 30.6 Gy with concomitant chemotherapy using capecitabine. The primary outcome of this trial is the R0 resection rate. Overall, GRECCAR 15 aims to recruit 186 patients to detect an absolute difference of 20% in the R0 resection rate with 80% power and 5% two-sided significance level.

CONCLUSION

The GRECCAR 15 trial is the first, definitive, phase III trial to investigate reirradiation in LRRC. The results of this trial will inform definitively the neoadjuvant treatment strategy in previously irradiated patients and assess whether there is any associated benefit of reirradiation in combination with induction chemotherapy in improving R0 resection rates.

Radiomic signature of the FOWARC trial predicts pathological response to neoadjuvant treatment in rectal cancer

Background

We aimed to develop a radiomic model based on pre-treatment computed tomography (CT) to predict the pathological complete response (pCR) in patients with rectal cancer after neoadjuvant treatment and tried to integrate our model with magnetic resonance imaging (MRI)-based radiomic signature.

Methods

This was a secondary analysis of the FOWARC randomized controlled trial. Radiomic features were extracted from pre-treatment portal venous-phase contrast-enhanced CT images of 177 patients with rectal cancer. Patients were randomly allocated to the primary and validation cohort. The least absolute shrinkage and selection operator regression was applied to select predictive features to build a radiomic signature for pCR prediction (rad-score). This CT-based rad-score was integrated with clinicopathological variables using gradient boosting machine (GBM) or MRI-based rad-score to construct comprehensive models for pCR prediction. The performance of CT-based model was evaluated and compared by receiver operator characteristic (ROC) curve analysis. The LR (likelihood ratio) test and AIC (Akaike information criterion) were applied to compare CT-based rad-score, MRI-based rad-score and the combined rad-score.

Results

We developed a CT-based rad-score for pCR prediction and a gradient boosting machine (GBM) model was built after clinicopathological variables were incorporated, with improved AUCs of 0.997 [95% CI 0.990–1.000] and 0.822 [95% CI 0.649–0.995] in the primary and validation cohort, respectively. Moreover, we constructed a combined model of CT- and MRI-based radiomic signatures that achieve better AIC (75.49 vs. 81.34 vs.82.39) than CT-based rad-score (P = 0.005) and MRI-based rad-score (P = 0.003) alone did.

Conclusions

The CT-based radiomic models we constructed may provide a useful and reliable tool to predict pCR after neoadjuvant treatment, identify patients that are appropriate for a 'watch and wait' approach, and thus avoid overtreatment. Moreover, the CT-based radiomic signature may add predictive value to the MRI-based models for clinical decision making.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-021-02919-x.

Surgical treatment of locally recurrent rectal cancer: a narrative review

Objective

To summarize the recent literature on surgical treatment of locally recurrent rectal cancer (LRRC).

Background

LRRC is a heterogeneous disease that requires a multidisciplinary treatment approach. The treatment and prognosis depend on the site and type of recurrence. Radical resection remains the primary method for achieving long-term survival and improving symptom control. Preoperative chemoradiotherapy can reduce tumor volume and improve the R0 resection rate. Surgeons must clearly understand pelvic anatomy, develop a detailed preoperative plan, adopt a multidisciplinary approach for the surgical resection of the tumor as well as any invaded soft tissues, vessels, and bones, and ensure proper reconstruction. However, extended radical surgery often leads to a higher risk of postoperative complications and a low quality of life.

Methods

We searched English-language articles with keywords “locally recurrent rectal cancer”, “surgery” and “multidisciplinary team” in PubMed published between January 2000 to October 2020.

Conclusions

LRRC is a complex problem. Long-term survival is not impossible following multidisciplinary treatment in appropriately selected LRRC patients. The management of LRRC relies on a specialist team that determines the biological behavior of the tumor and evaluates treatment options through multidisciplinary discussions, thereby balancing the surgical costs and benefits, alleviating postoperative complications, and improving patients’ quality of life.