Clinicopathologic features of South African colorectal cancer patients by HIV status in a retrospective cohort study.

3658 Background: Colorectal cancer (CRC) is increasing among people living with HIV. South Africa (SA) has the largest HIV-infected population in the world. Data characterizing the features of CRC among HIV patients in SA is limited. We compared the clinicopathologic features of CRC patients in SA by HIV-status. Methods: A retrospective cohort of CRC patients was identified using a database of histologically confirmed CRC patients seen at one of four referral hospitals in KwaZulu-Natal, SA between 2000 and 2024. Confirmed HIV-positive patients were randomly matched (1:2) with patients without HIV based on age at CRC diagnosis, year of CRC diagnosis, race, and tumor location. Additional clinical data was extracted through retrospective review of medical records. Chi-squared tests were used to compare features by HIV-status. Results: We identified 106 CRC patients with confirmed HIV-positive status and matched them with 155 CRC patients with confirmed HIV-negative status and 57 CRC patients with unknown HIV-status (assumed to be HIV-negative for analysis). At the time of CRC diagnosis, HIV-positive patients had an average duration of infection of 5.2 years and a mean baseline CD4 count of 451 cells/mm 3 . 72.6% of HIV patients were on antiretroviral therapy. HIV-status was not associated with duration of symptoms prior to CRC diagnosis (cohort mean 9.6 months; p-value = 0.687). HIV-positive patients were more likely than HIV-negative patients to present with metastatic disease (40.6% vs 28.8%, p-value = 0.035) and to have poorly differentiated tumors (13.9% vs 4.5%, p-value = 0.011). HIV-status was not associated with the rate of curative-intent treatment initiation (62.1% of non-metastatic patients received stage-appropriate treatment; p-value = 0.199) or palliative-intent systemic therapy (81.7% of metastatic patients received systemic therapy; p-value = 0.105). Conclusions: In SA, CRC patients with HIV are more likely than patients without HIV to present with high grade tumors and metastatic disease. This suggests a more aggressive tumor biology in this population. A comparison of overall survival by HIV-status will be presented at ASCO 2026. Future studies will compare the CRC tumor microenvironment by HIV-status in a subset of patients. Clinicopathologic features of colorectal cancer patients in South Africa by HIV-status (2000-2024). HIV-Positive(n = 106) HIV-Negative(n = 212) Total(n = 318) p-value Tumor Site 1.000 Colon 43 (40.6%) 86 (40.6%) 129 (40.6%) Rectal 63 (59.4%) 126 (59.4%) 189 (59.4%) Stage at Diagnosis 0.090 Early (I-IIa) 11 (10.4%) 32 (15.1%) 43 (13.5%) Locally Advanced (IIb-IIIc) 52 (49.1%) 119 (56.1%) 171 (53.8%) Metastatic (IVa-IVc) 43 (40.6%) 61 (28.8%) 104 (32.7%) Tumor Grade 0.040 Well Differentiated 2 (2.5%) 4 (2.6%) 6 (2.6%) Moderately Differentiated 66 (83.5%) 143 (92.9%) 209 (89.7%) Poorly Differentiated 11 (13.9%) 7 (4.5%) 18 (7.7%) Unknown 27 58 85