The future of TNM staging in rectal cancer: The era of neoadjuvant therapy

Evaluation and Predictive Factors of Complete Response in Rectal Cancer after Neoadjuvant Chemoradiation Therapy

The response to neoadjuvant chemoradiation therapy is an important prognostic factor for locally advanced rectal cancer. Although the majority of the patients after neoadjuvant therapy are referred to following surgery, the clinical data show that complete clinical or pathological response is found in a significant proportion of the patients. Diagnostic accuracy of confirming the complete response has a crucial role in further management of a rectal cancer patient. As the rate of clinical complete response, unfortunately, is not always consistent with pathological complete response, accurate diagnostic parameters and predictive markers of tumor response may help to guide more personalized treatment strategies and identify potential candidates for nonoperative management more safely. The management of complete response demands interdisciplinary collaboration including oncologists, radiotherapists, radiologists, pathologists, endoscopists and surgeons, because the absence of a multidisciplinary approach may compromise the oncological outcome. Prediction and improvement of rectal cancer response to neoadjuvant therapy is still an active and challenging field of further research. This literature review is summarizing the main, currently known clinical information about the complete response that could be useful in case if encountering such condition in rectal cancer patients after neoadjuvant chemoradiation therapy, using as a source PubMed publications from 2010–2021 matching the search terms “rectal cancer”, “neoadjuvant therapy” and “response”.

Prevalence of nodal involvement in rectal cancer after chemoradiotherapy

BACKGROUND

The purpose of this study was to investigate the prevalence of ypN+ status according to ypT category in patients with locally advanced rectal cancer treated with chemoradiotherapy and total mesorectal excision, and to assess the impact of ypN+ on disease recurrence and survival by pooled analysis of individual-patient data.

METHODS

Individual-patient data from 10 studies of chemoradiotherapy for rectal cancer were included. Pooled rates of ypN+ disease were calculated with 95 per cent confidence interval for each ypT category. Kaplan-Meier and Cox regression analyses were undertaken to assess influence of ypN status on 5-year disease-free survival (DFS) and overall survival (OS).

RESULTS

Data on 1898 patients were included in the study. Median follow-up was 50 (range 0-219) months. The pooled rate of ypN+ disease was 7 per cent for ypT0, 12 per cent for ypT1, 17 per cent for ypT2, 40 per cent for ypT3, and 46 per cent for ypT4 tumours. Patients with ypN+ disease had lower 5-year DFS and OS (46.2 and 63.4 per cent respectively) than patients with ypN0 tumours (74.5 and 83.2 per cent) (P < 0.001). Cox regression analyses showed ypN+ status to be an independent predictor of recurrence and death.

CONCLUSION

Risk of nodal metastases (ypN+) after chemoradiotherapy increases with advancing ypT category and needs to be considered if an organ-preserving strategy is contemplated.

How to measure tumour response in rectal cancer? An explanation of discrepancies and suggestions for improvement

Various methods categorize tumour response after neoadjuvant therapy, including down-staging and tumour regression grading. Response categories allow comparison of different treatments within clinical trials and predict outcome. A reproducible response categorization could identify subgroups with high or low risk for the most appropriate subsequent treatments, like watch and wait. Lack of standardization and interpretation difficulties currently limit the usability of these approaches. In this review we describe these difficulties for the evaluation of chemoradiation in rectal cancer. An alternative approach of tumour response is based on patterns of residual disease, including fragmentation. We summarise the evidence behind this alternative method of response categorisation, which explains a number of very relevant clinical discrepancies. These issues include differences between downstaging and tumour regression, high local regrowth in advanced tumours during watchful waiting procedures, the importance of resection margins, the limited value of post-treatment biopsies and the relatively poor outcome of patients with a near complete pathological response. Recognition of these patterns of response can allow meaningful development of novel biomarkers in the future.

TNM-O: ontology support for staging of malignant tumours

BACKGROUND

Objectives of this work are to (1) present an ontological framework for the TNM classification system, (2) exemplify this framework by an ontology for colon and rectum tumours, and (3) evaluate this ontology by assigning TNM classes to real world pathology data.

METHODS

The TNM ontology uses the Foundational Model of Anatomy for anatomical entities and BioTopLite 2 as a domain top-level ontology. General rules for the TNM classification system and the specific TNM classification for colorectal tumours were axiomatised in description logic. Case-based information was collected from tumour documentation practice in the Comprehensive Cancer Centre of a large university hospital. Based on the ontology, a module was developed that classifies pathology data.

RESULTS

TNM was represented as an information artefact, which consists of single representational units. Corresponding to every representational unit, tumours and tumour aggregates were defined. Tumour aggregates consist of the primary tumour and, if existing, of infiltrated regional lymph nodes and distant metastases. TNM codes depend on the location and certain qualities of the primary tumour (T), the infiltrated regional lymph nodes (N) and the existence of distant metastases (M). Tumour data from clinical and pathological documentation were successfully classified with the ontology.

CONCLUSION

A first version of the TNM Ontology represents the TNM system for the description of the anatomical extent of malignant tumours. The present work demonstrates its representational power and completeness as well as its applicability for classification of instance data.

Predicting lymph node metastases in pT1 rectal cancer

With the widespread introduction of population screening for colorectal cancer in Europe, the number of early rectal cancers is expected to increase. In the past, approximately 25 % of rectal cancers presented with early disease, defined as stage I disease. First, results from population screening in the UK demonstrate an increase to approximately 50 % stage I for screen-detected carcinomas. In the absence of lymph node metastases, local excision of the tumor might be an attractive option, with considerably less morbidity due to surgery and a lower mortality. This option demonstrates the need for a reliable method of lymph node metastasis prediction in early rectal cancer. The overall risk of lymph node metastasis in pT1 tumors is still considerable, 11.4 %. In order to avoid both under-and overtreatment, we need adequate risk factors.

Partial pathologic response and nodal status as most significant prognostic factors for advanced rectal cancer treated with preoperative chemoradiotherapy

BACKGROUND

This study evaluated the impact of tumor regression grading (TRG) and other pathologic variates in a cohort of rectal carcinoma patients treated with neoadjuvant chemoradiotherapy (CRT). The value of a grading less than pCR for predicting survival is unknown. Tumor budding has not been systematically studied in rectal cancer after neoadjuvant therapy.

METHODS

Pathologic risk factors for survival were evaluated on surgical specimens of 237 patients with stages I, II, and III rectal cancer treated between 1996 and 2006. All patients underwent preoperative CRT followed by surgical resection 6-8 weeks later. TRG, tumor grade, budding, venous invasion, radial margin, and nodal status were evaluated. The prognostic value of TRG categories was calculated with Cox regression models and validated with resampling methods.

RESULTS

TRG of <25% occurred in 61 (25.7%) and a complete response in 39 (16.4%) of the resected specimens. TRG of <25% was shown to be a statistically significant predictor for cancer-specific survival (CSS) and recurrence-free survival (RFS) compared to TRG ≥25% (P = 0.013). Tumor budding was present in 24 (10.1%) of the patients and was negatively associated with CSS (P = 0.013). Lymph node involvement was observed in 83 (35.0%) patients. TRG and nodal status (P < 0.001) were the most significant predictors associated with outcome.

CONCLUSION

Partial pathologic response ≥25% was a superior predictor compared to pCR for improved survival after preoperative CRT. CSS and RFS were adversely affected by the presence of lymph node metastases.

Has the new TNM classification for colorectal cancer improved care?

In 2009, the Union for International Cancer Control issued the seventh edition of the well-used T (tumor), N (node), and M (metastasis) classification guidelines. There has been a continual refinement of the staging for colorectal cancer since this system for assessing tumor stage was initially adopted and it has been used to guide treatment decisions for over 50 years. However, the outcome after therapy for patients with colorectal cancer is very variable, even when patients are assigned to the same TNM category. This article assesses the changes that have been made since the sixth edition and discusses whether they are, in fact, informative improvements for a practicing clinician.