Chemoradiation therapy (CRT) followed by surgery is currently the standard of care to treat patients with locally advanced rectal cancer (LARC). CRT reduces local recurrences, but is associated with significant damage to the surrounding healthy tissue that can severely impact quality of life. Additionally, a proportion of patients (hardly) benefit from CRT. We aim to develop a diagnostic innovation, which can enable a more selective and thereby more effective use of the available therapies for rectal cancer patients.

The objective of this study is to investigate whether patients can be identified who will response to CRT prior to start of the CRT in rectal cancer and therefore avoid possible severe side effects in patients who will not reponse on CRT.

Inclusion Criteria:

• Age ≥18 years
• Histologically confirmed rectal adenocarcinoma
• Scheduled for neoadjuvant chemoradiation
• Written informed consent.

Exclusion Criteria:

• Scheduled to another neoadjuvant schedule that comprises systemic chemotherapy or short-course radiation
• Not able to read or understand Dutch language or mentally not capable.

Locally advanced rectal cancer patients scheduled for preoperative chemoradiation