Bowel cancer is the fourth most commonly occurring cancer and the second highest cause of cancer deaths in the UK. Despite advances in treatment, over 40% of patients will die within 5 years. This is normally due to spread of the cancer to other organs (called metastases). Much of the current research focuses on use of additional treatments such as radiotherapy and chemotherapy before or after surgery (adjuvant treatment). It is of vital importance that patients who would benefit from adjuvant treatment can be accurately identified. At the moment, the system used locally to do this places emphasis on the presence of affected lymph nodes (glands). This is because doctors believe that cancer spreads to other organs through the lymphatic system. However, recent studies have suggested that this is not the case.

It is believed that cancer spreads to other organs through the blood stream rather than the lymph node system. This research will look at the genetic material in tumours and metastases as well as in areas of blood vessel invasion and lymph nodes. The analysis will allow us to build a 'family tree' of the tumour and allow us to map the pathway by which the tumour spreads. Tissue samples already collected through a patient's routine care will be used for this study. If the spread through the blood vessels is proven, this would change the way in which patients are selected for treatment and allow development of new treatments to target these pathways.

A retrospective ,non-interventional tissue study using archival materials collected through a patient's routine care, EVIDENCE aims to demonstrate that distant metastases in colorectal cancer are related to Extramural Venous Invasion (EMVI) and tumour deposits, not lymph nodes. As EVIDENCE is a retrospective study, there are no time dependent schedules for Case Report Form (CRF) completion or tissue submission.

It will be tested whether the vascular route of spread (as evidenced through EMVI and tumour deposits) is more important than lymph nodes in the development of metastatic disease. The sub-clonal origins of primary colorectal cancers, EMVI, tumour deposits, lymph nodes and distant metastases by reconstructing phylogenetic trees will be compared. A proof for a vascular route of spread rather than lymph nodes would lead to a paradigm shift in future decision making at national and international level.

Inclusion Criteria:

1. Are aged 16 years or over with colorectal cancer
2. Colon / rectum has been surgically removed
3. Distant metastases has been surgically removed
4. Pre operative staging in the form of CT/MRI has been undertaken and images available for review

Exclusion Criteria:

1. Pathological complete response in the primary tumour
2. Local resection of the primary tumour
3. Inadequate quantity of tissue sample to perform analyses

Patients who have undergone a primary resection of their colon or rectum as well as a resection of a distant metastases