Clinical Study on the Expression of PHGDH and Its Prognostic Value in Colorectal Cancer Patients Receiving Immunotherapy

• No intervention (Other): No therapeutic or experimental intervention was administered in this study. Participants were assigned to the PHGDH-high and PHGDH-low cohorts according to PHGDH expression in tumor tissues for observational analysis of clinical outcomes and treatment response.

Primary outcomes

• Objective Response Rate (ORR) [Assessed at 3 months after initiation of immunotherapy.]: Proportion of participants achieving a complete response (CR) or partial response (PR) per RECIST v1.1 criteria.

Secondary outcomes

• Progression-Free Survival (PFS) [Time Frame: From the start of treatment until the first progression event or the end of follow-up (assessed up to 36 months).]: Time from the first dose of immune checkpoint inhibitor therapy to radiographic disease progression as per RECIST v1.1 criteria or death from any cause, whichever occurs first.

Sex: All

Inclusion Criteria:

1. Patients with histologically confirmed colorectal adenocarcinoma.
2. Initiated treatment with immune checkpoint inhibitors (at least one cycle) between June 1, 2018 and December 31, 2025.
3. Availability of pre-treatment archival tumor tissue (FFPE block or slides) for PHGDH immunohistochemistry testing.
4. Have evaluable baseline radiographic images (CT or MRI) prior to immunotherapy.
5. Sufficient medical records for survival follow-up data extraction.

Exclusion Criteria:

1. Unavailability of adequate tumor tissue for PHGDH expression analysis.
2. Permanently discontinued immunotherapy prior to the first scheduled radiological response assessment.
3. History of other active malignancies within the past 5 years (except for adequately treated basal cell carcinoma of the skin or carcinoma in situ of the cervix).
4. Insufficient clinical documentation to determine the primary outcome (e.g., progression-free survival).