*10.3.1 Percentage viable tumour*

Microscopic assessment of the percentage residual viable tumour on haematoxylin & eosin-stained sections of resected tissue has been employed as a predominant parameter in assessing the efficacy of different pre-operative chemotherapy regimens in tumour types such as oesophageal, gastric and rectal adenocarcinomas [113]. Based on this methodology, Ribero and colleagues modified this scoring system for application in CRLMs treated preoperatively, with or without bevacizumab [114]. A semi-quantitative estimation of the percentage area of residual viable tumour cells relative to total tumour surface area within each CRLM metastasis was made with the analysis of four tumour cell viability subsets (<25%, 25–49%,

**55**

**Figure 3.**

*DOI: http://dx.doi.org/10.5772/intechopen.89667*

*10.3.2 Tumour regression grade (TRG)*

*Angiogenesis and Its Role in the Tumour Microenvironment: A Target for Cancer Therapy*

50–75%, >75%). This retrospective study confirmed that the addition of bevacizumab to chemotherapy yielded an incrementally greater decrease in residual viable cells within these CRLMs in comparison to those treated with chemotherapy alone but no correlation with imaging, or other clinical end-points, was made [114].

Mandard and colleagues were one of the first to establish a five-point histological scoring system for pathological response. This was based on cytological and stromal changes on haematoxylin & eosin-stained sections of primary oesophageal squamous cell carcinomas treated with chemoradiotherapy prior to resection [115].

*Tumour regression grade (TRG) scoring system as a component of measuring pathological response in treated CRLMs. (A–E) TRG as scored on haematoxylin and eosin sections of CRLMs based on the proportion of fibrosis to viable tumour cells. The five TRGs shown in this cartoon roughly illustrate the different proportions of fibrosis (fibrils) to tumour cells (black areas). (A) TRG1. There is an absence of viable tumour cells and large amounts of fibrosis. (B) TRG2. The presence of viable tumour cells is rare and they are scattered throughout the fibrosis. (C) TRG3. There is the presence of more residual tumour cells but fibrosis predominates. (D) TRG4. Residual cancer cells predominate over fibrosis. (E) TRG5. There are no signs of tumour regression. The percentage of the CRLM surface area occupied by necrosis is also incorporated as a parameter for pathological response (grey areas). 3 main pathological response groups: TRG1-2: major response* 

*(MjHR), TRG3: partial response (PHR), TRG4-5: no histological response (NHR).*

*DOI: http://dx.doi.org/10.5772/intechopen.89667 Angiogenesis and Its Role in the Tumour Microenvironment: A Target for Cancer Therapy*

50–75%, >75%). This retrospective study confirmed that the addition of bevacizumab to chemotherapy yielded an incrementally greater decrease in residual viable cells within these CRLMs in comparison to those treated with chemotherapy alone but no correlation with imaging, or other clinical end-points, was made [114].
