How reliable is restaging MRI after neoadjuvant therapy in rectal cancer?

The predicting value of post neoadjuvant treatment magnetic resonance imaging: a meta-analysis

INTRODUCTION

Neoadjuvant therapy has become standard of care for locally advanced rectal cancer patients. It is correlated with improved clinical and pathological outcomes, including significant tumor downstaging and organ preservation in certain patients. Magnetic resonance imaging (MRI), which has become the standard for pre-operative staging, is also used for clinical and pre-operative restaging following pre-operative treatment. In this meta-analysis, we aimed to evaluate the concordance between restaging MRI (following the completion of neoadjuvant therapy) and postoperative pathology result.

METHODS

We conducted a meta-analysis following the PRISMA 2020 guidelines. Two independent reviewers searched PubMed and Google Scholar for studies reporting restaging MRI results compared to pathological outcomes. Outcomes included tumor and nodal staging, circumferential resection margin (CRM) and pathological complete response (pCR).

RESULTS

Out of 25,000 studies found on the initial search; 33 studies were included. The studies were published between 2005 and 2023 and included 4100 patients (57.14% males). The median age was 62.45 years. The median interval between the conclusion of neoadjuvant treatment and the subsequent restaging MRI was 6 weeks (range 4.14-8.8 weeks). The pooled concordance rates between the restaging MRI and the pathological outcomes for ypT stage and ypN stage were 63.9% (54.5%-73.3%, I2 = 96.02%) and 60.9% (42.9%-78.9%, I2 = 98.96%), respectively. The pooled concordance for predicting pathological complete response was 70.4% (53.6%-87.1%, I2 = 98.21%). As for the circumferential resection margin (CRM), the pooled concordance was 78.2.% (71.6%-84.8%, I2 = 83.76%).

CONCLUSIONS

Our findings suggest that the concordance rates between restaging MRI and pathological outcomes in rectal cancer patients following neoadjuvant therapy are limited. Caregivers should take these results into consideration when making clinical decisions about these patients. More data should be gathered about the predictive value of MRI after total neoadjuvant therapy as well as immunotherapy in rectal cancer patients.

The Role of Predictive and Prognostic MRI-Based Biomarkers in the Era of Total Neoadjuvant Treatment in Rectal Cancer

The role of magnetic resonance imaging (MRI) in rectal cancer management has significantly increased over the last decade, in line with more personalized treatment approaches. Total neoadjuvant treatment (TNT) plays a pivotal role in the shift from traditional surgical approach to non-surgical approaches such as 'watch-and-wait'. MRI plays a central role in this evolving landscape, providing essential morphological and functional data that support clinical decision-making. Key MRI-based biomarkers, including circumferential resection margin (CRM), extramural venous invasion (EMVI), tumour deposits, diffusion-weighted imaging (DWI), and MRI tumour regression grade (mrTRG), have proven valuable for staging, response assessment, and patient prognosis. Functional imaging techniques, such as dynamic contrast-enhanced MRI (DCE-MRI), alongside emerging biomarkers derived from radiomics and artificial intelligence (AI) have the potential to transform rectal cancer management offering data that enhance T and N staging, histopathological characterization, prediction of treatment response, recurrence detection, and identification of genomic features. This review outlines validated morphological and functional MRI-derived biomarkers with both prognostic and predictive significance, while also exploring the potential of radiomics and artificial intelligence in rectal cancer management. Furthermore, we discuss the role of rectal MRI in the 'watch-and-wait' approach, highlighting important practical aspects in selecting patients for non-surgical management.

Effect of neoadjuvant therapy regimens on lymph nodes yield in rectal cancer

BACKGROUND AND OBJECTIVES

Pathological nodal staging is relevant to postoperative decision-making and a prognostic marker of cancer survival. This study aimed to assess the effect of different total neoadjuvant therapy (TNT) regimens on lymph node status following total mesorectal excision (TME) for locally advanced rectal cancer (LARC).

METHODS

A retrospective cohort study of patients treated for node-positive clinical stage 3 LARC with TNT between January 2015 and August 2022. Patients were stratified into induction therapy and consolidation therapy groups. Variables collated included patient demographics, clinical and radiological characteristics of the tumor, and pathology of the resected specimen. Primary outcome was total harvested lymph nodes.

RESULTS

Ninety-seven patients were included (57 [58.8%] males; mean age of 58.5 ± 11.4 years). The induction therapy group included 85 (87.6%) patients while 12 (12.4%) patients received consolidation therapy. A median interquartile range value of 22.00 (5.00-72.00) harvested lymph nodes was recorded for the induction therapy group in comparison to 16.00 (16.00-47.00) in the consolidation therapy arm (p = 0.487). Overall pathological complete response rate was 34%.

CONCLUSION

Total harvested nodes from resected specimens were marginally lower in the consolidation therapy group. Induction therapy may be preferrable to optimize postoperative specimen staging.

Compare clinical efficacy and safety of neoadjuvant therapy and neoadjuvant chemoradiotherapy for locally advanced rectal cancer: Meta-analysis

BACKGROUND

To compare the efficacy and safety of total neoadjuvant therapy (TNT) and neoadjuvant chemoradiotherapy (nCRT) in the treatment of middle and low locally advanced rectal cancer. Our study will systematically collect and integrate studies to evaluate the ability of these two treatments to improve tumor shrinkage rates, surgical resection rates, tumor-free survival, and severe adverse events.

AIM

To provide clinicians and patients with more reliable treatment options to optimize treatment outcomes and quality of life for patients with locally advanced rectal cancer by comparing the advantages and disadvantages of the two treatment options.

METHODS

A full search of all clinical studies on the effectiveness and safety of TNT and nCRT for treating locally advanced rectal cancer identified in Chinese (CNKI, Wanfang, China Biomedical Literature Database) and English (PubMed, Embase) databases was performed. Two system assessors independently screened the studies according to the inclusion and exclusion criteria. Quality evaluation and data extraction were performed for the included literature. We used RevMan 5.3 software to perform a meta-analysis of the pathologic complete response (pCR) rate, T stage degradation rate, resection 0 (R0) rate, anal grade 3/4 acute toxicity rate, perioperative complications, overall survival (OS), and disease-free survival (DFS) in the TNT and nCRT groups.

RESULTS

Finally, 14 studies were included, six of which were randomized controlled studies. A total of 3797 patients were included, including 1865 in the TNT group and 1932 in the nCRT group. The two sets of baseline data were comparable. The results of the meta-analysis showed that the pCR rate [odds ratio (OR) = 1.57, 95% confidence interval (CI): 1.30-1.90, P < 0.00001], T stage degradation rate (OR = 2.16, 95%CI: 1.63-2.57, P < 0.00001), and R0 resection rate (OR = 1.42, 95%CI: 1.09-1.85, P = 0.009) were significantly greater in the nCRT group than in the nCRT group. There was no significant difference in the incidence of grade 3/4 acute toxicity or perioperative complications between the two groups. The 5-year OS [hazard ratio (HR) = 0.84, 95%CI: 0.69-1.02, P = 0.08] and DFS (HR = 0.94, 95%CI: 0.03-1.39, P = 0.74) of the TNT group were similar to those of the nCRT group.

CONCLUSION

TNT has greater clinical efficacy and safety than nCRT in the treatment of locally advanced rectal cancer.

Non-operative management of rectal cancer: Highlighting the controversies

There remains much ambiguity on what non-operative management (NOM) of rectal cancer truly entails in terms of the methods to be adopted and the best algorithm to follow. This is clearly shown by the discordance between various national and international guidelines on NOM of rectal cancer. The main aim of the NOM strategy is organ preservation and avoiding unnecessary surgical intervention, which carries its own risk of morbidity. A highly specific and sensitive surveillance program must be devised to avoid patients undergoing unnecessary surgical interventions. In many studies, NOM, often interchangeably called the Watch and Wait strategy, has been shown as a promising treatment option when undertaken in the appropriate patient population, where a clinical complete response is achieved. However, there are no clear guidelines on patient selection for NOM along with the optimal method of surveillance.

Comparison of preoperative magnetic resonance imaging with postoperative pathology results in rectal cancer patients undergoing neoadjuvant therapy

BACKGROUND

Locally advanced rectal cancer often requires neoadjuvant treatment (NAT) before surgical intervention. This study aimed to assess the concordance between preoperative magnetic resonance imaging (MRI) findings and postoperative pathology results after NAT in rectal cancer patients.

METHOD

A retrospective analysis of 52 patients who underwent NAT and subsequent surgery at Ankara Bilkent City Hospital between May 2019 and May 2023 was conducted. Demographics, preoperative MRIs, time intervals between NAT, MRI, and surgery, and postoperative pathology were assessed.

RESULTS

The median age of the cohort was 59 years, with a male predominance (76.9%). Tumour T stage (κ = 0.157), lymph node stage (κ = 0.138), and circumferential resection margin (κ = 0.138) concordance showed poor agreement between post-neoadjuvant treatment (PNT) MRI and pathology. PNT MRI demonstrated a limited correlation with postoperative pathology.

CONCLUSIONS

While preoperative MRI is commonly used for restaging after NAT in rectal cancer, our study highlights its limited concordance with postoperative pathology. The sensitivity and specificity metrics, although reported in the literature, should be interpreted alongside concordance assessments for a comprehensive evaluation.

Operative trends following the adoption of nonoperative management of rectal cancer

BACKGROUND

Differentiating clinical near-complete and complete responses (cCR) after neoadjuvant therapy (NT) is challenging in rectal cancer patients. We hypothesized that magnetic resonance imaging staging limitations for low rectal cancers may increase the proportion of abdominoperineal resection (APR) with permanent colostomy for those without a cCR.

METHODS

Single institution retrospective analysis of rectal cancer cases before and after adoption of nonoperative "watch and wait" (W&W) pathway. APR as a percentage of rectal resections was the primary outcome.

RESULTS

There were 76 total mesorectal excisions (TME) in the pre-W&W group and 98 in the post-W&W group. NT was significantly more common in the post-W&W group. There was no significant difference in the APR primary outcome (pre-W&W APR 33.3% vs. post-W&W APR 26.5%, p = 0.482). APR patients had fewer complete TME grades (69.2% vs. 46.2%) and more pathologic complete responses (0% vs. 26.9%) in the post-W&W period. The cCR rate for patients with nonoperative management was 51.4% (n = 37) and 13.5% (n = 5) had regrowths, all of whom underwent salvage surgery.

CONCLUSION

APR for those without a cCR to NT has not increased in the nonoperative management era. Balancing the pathologic complete response rate may require restaging some patients with clinical near-complete responses.