An investigation into the relationship between the tumour and its environment and survival in patients with operable colorectal cancer

Colorectal cancer is the second most common cause of cancer death in the Western World. Although staging and prognosis is presently based on pathological assessment of primary tumour invasion and the presence of lymph node and distant metastases, it is increasingly recognised that other factors pertaining to both the tumour and host may similarly affect outcome. The local and systemic environment, encompassing host inflammatory responses and the tumour microenvironment, are examples of such. However, how such measures may compliment present TNM-based staging are not clear. Furthermore, tumour and host factors, both modifiable and non-modifiable, which may determine the local and systemic environment, remain to be fully determined. The present thesis examined the clinical and prognostic utility of assessment of the local and systemic environment, and potential tumour and host factors which may determine these responses. The following conclusions were drawn: Examining patients from the United Kingdom and Japan, Chapter 2 and 3 concluded that assessment of the systemic inflammatory response, utilising the modified Glasgow Prognostic Score, provides further prognostic stratification in addition to TNM stage. Although the proportion of patients exhibiting an elevated systemic inflammatory response differed between populations, the prognostic value was comparable. Chapter 4 validated assessment of the tumour stroma percentage as a prognostic factor independent of TNM stage and the local inflammatory cell infiltrate (cancer-specific survival HR 1.84, 95% CI 1.17-2.92, P=0.009). Chapter 7 further confirmed the prognostic value of a combined tumour microenvironment score, based on assessment of the generalised inflammatory cell infiltrate and tumour stroma percentage, in patients with primary operable colorectal cancer. This score, termed the Glasgow Microenvironment Score, was able to stratify patients into a good prognostic group, with five-year survival of 89%, an intermediate group with a two-fold increased risk of death and five-year survival of 75%, and a poor prognostic group, with a four-fold increased risk of death and five-year survival of 51%. Chapters 5 and 6 identified the presence of mismatch repair deficiency and activation of the JAK/STAT3 as two potential mechanisms which may determine host local and systemic inflammatory responses. However, the prognostic value of such candidate mechanisms was weak, suggesting that other pathways and tumour characteristics are implicated, and that molecular heterogeneity is likely to play an important role in determining not only the local and systemic environment, but also outcome. Chapter 9 concluded that the Immunoscore, an immunohistochemistry-based assessment of T-lymphocyte density within the tumour microenvironment, held greater prognostic value than assessment of the generalised inflammatory cell infiltrate using the Klintrup-Mäkinen grade. However, assessment of tumour stroma percentage provided additional prognostic value irrespective of the methodology employed to examine the local inflammatory cell infiltrate. Furthermore, the results of Chapters 7, 8 and 9 together suggested that loss of the local, anti-tumour immune infiltrate was the primary event which allows continued tumour growth, development of a tumour-supportive microenvironment and propagation of a systemic inflammatory response. Chapter 10 concluded that pre-diagnosis use of aspirin but not statins was associated with a lower modified Glasgow Prognostic Score, despite strong associations with comorbidity and BMI. This did not translate into an improvement in survival, potentially reflecting the underlying indication for use of these drugs primarily as cardiovascular secondary prevention medications. Finally, Chapter 11 examined the clinical utility of assessment of the tumour microenvironment using colonoscopic biopsy specimens, concluding that the use of biopsy-derived specimens was feasible. Furthermore, in addition to identifying patients who may benefit from therapies targeting the tumour microenvironment, assessment of a biopsy-derived Glasgow Microenvironment Score had comparable prognostic value to full section assessment of the tumour microenvironment