Recent research shows that tumour deposits-small spots of cancer found near the main bowel tumour-may give doctors important information about how aggressive the cancer is and how likely it is to come back.

Doctors can find tumour deposits either:

1. When looking at scans before surgery, or
2. when examining the removed bowel tissue under the microscope after surgery.

In the past, tumour deposits were not always recorded properly. This is because older cancer-staging systems (called TNM 5) used in the UK treated these spots differently, depending on their size, and sometimes labelled them as lymph nodes even when they were not. As a result, many tumour deposits were missed in reports.

Since 2018, the UK has been using an updated staging system (called TNM 8) that gives tumour deposits their own category. This means doctors are now expected to report them separately when they are found in the tissue around the bowel.

This matters because the investigators know that patients who have tumour deposits may have a higher risk of the cancer returning or spreading. Because of this, these patients might benefit from extra treatment-such as chemotherapy or radiotherapy-on top of surgery.

However, if tumour deposits are not routinely recorded on scans or pathology reports, doctors may not realise a patient has them. This means that:

1. Patients may not get the most appropriate advice about their cancer, and
2. Patients may miss out on treatments that could help reduce the chance of the cancer returning.

This research project aims to find out two things:

1. Are tumour deposits being routinely reported on scans and pathology reports for rectal cancer since the newer TNM 8 system was introduced? And
2. Is there a link between reporting tumour deposits and another important finding called EMVI (extramural vascular invasion), which also affects cancer behaviour and treatment decisions?

Background:

There is increasing evidence that Tumour Deposits (TDs) play an important role in determining prognosis in colorectal cancer patients, both on pathology and on pre-operative imaging (1-2). There is a great variation in their reported prevalence on pathology (1) depending on the staging system and pathology techniques used. Previous work to determine the prevalence of TDs in the UK has relied on the TNM 5 classification, since the 6th and 7th editions were not adopted into UK practice. In TNM 5, all tumour nodules of >3mm were classified as lymph nodes, regardless of whether there was evidence of underlying nodal architecture. Nodules of under 3mm were included in the T stage. Reporting of TDs only took place if the pathologist made specific mention of them in the body of the report, therefore the reported prevalence was very low (6%) compared to when detected on imaging (36%)(2). TNM 8, released in 2017, is the current Tumour Node Metastases staging system used for colorectal cancer (3) and was adopted in the UK from January 2018 onwards. In TNM 8 however, TDs in the subserosa, or in non-peritonealised pericolic or perirectal soft tissue without regional lymph node metastatic disease are reported as N1c. The aim of this multicentre retrospective evaluation is to understand if TDs are being routinely reported in imaging and pathology in rectal cancer patients since the introduction of TNM 8.

Rationale:

There is increasing evidence that TDs impact the recurrence of cancer and cancer death in patients with rectal cancer for the worse. These patients may therefore benefit from additional treatment with chemotherapy or radiotherapy. However, if we are not recording TDs routinely, and don't know at the time of deciding how to treat these patients that they have TDs, then we are not counselling patients properly as well as may not be offering them additional chemotherapy or radiotherapy.

Objectives:

Primary Objectives:

To determine whether, since the introduction of TNM 8, TDs are being routinely reported in staging of rectal cancer on imaging and pathology

Secondary Objective:

To determine if there is as positive association between the reporting of TDs and the reporting of Extramural Venous Invasion.

References:

Please see separate References Section

Inclusion Criteria:

1. Primary adenocarcinoma of the rectum (proven by biopsy)
2. Undergone surgical resection between 01st January 2007 to 31st December 2017 inclusive for the TNM 5 cohort
3. Undergone surgical resection between 01st January 2022 to 31st December 2024 inclusive for the TNM 8 cohort

3. Staging with MRI reports are available 4. Post-operative pathology report available 5. Patients aged 16 years and over

Exclusion Criteria:

1. Synchronous metastatic tumours
2. Under the age of 16 years
3. MRI and/or pathology reports are not available

Patients (>16 years old) with primary adenocarcinoma of the rectum who have undergone resectional surgery

IPD used in the results publication will be shared. At the time of publication of results, fully anonymised data will be made available to those that request it upon reasonable request.

Study protocol which includes the statistical analysis plan is available for sharing immediately. Results will be available at the time of publication.

Anyone will be able to access the IPD and supporting information. The will be able to access the study protocol which includes the statistical analysis plan and anonymised individual participant data. They can access it by emailing Prof. Brown or Harpreet Sekhon at gina.brown@imperial.ac.uk, giclinicaltrials@imperial.ac.uk or hks224@ic.ac.uk Alternatively, it will be released onto the ClinicalTrials.gov record at the time of Results publication