['colorectal cancer']
['tremelimumab', 'durvalumab']

        Inclusion Criteria:

          -  Must have histologically or pathologically confirmed advanced (metastatic or locally
             advanced) colorectal cancer that is unresectable.

          -  Received a prior thymidylate synthase inhibitor (e.g. 5-fluorouracil (5-FU),
             capecitabine, raltitrexed, UFT) for metastatic disease or as adjuvant therapy. A
             thymidylate synthase inhibitor may have been given in combination with oxaliplatin or
             irinotecan.

          -  Received and failed an irinotecan -containing regimen (i.e. single-agent or in
             combination) for treatment of metastatic disease, OR relapsed within 6 months of
             completion of an irinotecan-containing adjuvant therapy, OR have documented
             unsuitability for an irinotecan-containing regimen.

          -  Received and failed an oxaliplatin-containing regimen (i.e. single-agent or in
             combination) for treatment of metastatic disease, OR relapsed within 6 months of
             completion of an oxaliplatin-containing adjuvant therapy OR have documented
             unsuitability for an oxaliplatin-containing regimen.

          -  For patients with colorectal cancer that is RAS-wild type:

        Received and failed a cetuximab or panitumumab-containing regimen (i.e. single-agent or in
        combination) for treatment of metastatic disease OR have documented unsuitability for a
        cetuximab or panitumumab-containing regimen

          -  Patient prior treatment with VEGF targeting therapy, such as bevacizumab, aflibercept,
             ramucirumab, or regorafenib, is permitted but not mandatory. Reasons not used are to
             be documented.

          -  Patient prior treatment with TAS-102 (an agent composed of a combination of
             trifluorothymidine (FTD) and tipiracil hydrochloride (TPI)), is permitted but not
             mandatory.

          -  The only remaining standard available therapy as recommended by the Investigator, in
             consultation with the patient, is best supportive care.

          -  Must have presence of measurable or evaluable disease as defined by Response
             Evaluation Criteria in Solid Tumours (RECIST 1.1).

          -  Imaging investigations including CT/MRI of chest/abdomen/pelvis or other scans as
             necessary to document all sites of disease done within 28 days prior to randomization.

          -  Must have an Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1.

          -  Life expectancy of ≥ 12 weeks at the time of study entry.

          -  Must be ≥ 18 years of age.

          -  Women/men of childbearing potential must have agreed to use a highly effective
             contraceptive method.

          -  Patient must consent to provision of, and investigator(s) must confirm adequacy of
             tissue, and confirm access to and agree to submit within 4 weeks of randomization to
             the CCTG Central Tumour Bank, a representative formalin fixed paraffin block of tumour
             tissue in order that the specific correlative marker assays may be conducted.

          -  Patient must consent to provision of samples of blood in order that the specific
             correlative marker assays

          -  Patient is able (i.e. sufficiently fluent) and willing to complete the quality of life
             questionnaires in either English or French.

        Patients must be accessible for treatment and follow-up. Investigators must assure
        themselves the patients randomized on this trial will be available for complete
        documentation of the treatment, adverse events, and follow-up.

          -  In accordance with CCTG policy, protocol treatment is to begin within 2 working days
             of patient randomization.

          -  The patient is not receiving therapy in a concurrent clinical study and the patient
             agrees not to participate in other clinical studies during their participation in this
             trial while on study treatment.
      