Racial and ethnic disparities in the occurrence of second primary malignancies (SPMs) in early onset colorectal cancer (EOCRC).

e15685 Background: Early-onset colorectal cancer (EOCRC) (diagnosed before age 50) has been increasing in the United States, prompting a recent change in screening guidelines to begin at age 45. With a growing population of younger cancer survivors, our study aims to evaluate the risk of second primary malignancies (SPMs) and racial disparity in this group to enhance survivorship care and long-term health outcomes. Methods: We performed a retrospective analysis of the Surveillance, Epidemiology and End Results (SEER) 17 registries database to identify the cases diagnosed with EOCRC as primary malignancy from 2000 to 2021. The standardized incidence ratios (SIR) for the development of SPMs in EOCRC were obtained. The analysis was stratified by the following races and ethnicities: Non-Hispanic Whites (NHW), Non-Hispanic Blacks (NHB), Non-Hispanic American Indian/Non-Hispanic Alaska Native (NHAIAN), Non-Hispanic Asian or Pacific Islander (NHAPI), Hispanic (H). Results: A total of 76,935 EOCRC survivors were included (58% NHW, 13% NHB, 0.76% NHAIAN, 10% NHAPI, and 18% H). A total of 71, 299 cancers occurred during ages 30-49. There was an elevated risk for stomach, small intestine, urinary bladder, and thyroid SPMs in all groups except NHAIAN, with statistically significant SIRs (p < 0.05) (table). All groups had a statistically significant increased risk for kidney cancers except NHAPI, with SIRs (p < 0.05) in decreasing order as follows: NHAIAN 8.22, H 2.27, NHB 2.18, and NHW 1.8. The risk for lung/bronchus SPMs is statistically significant in NHAIAN, NHAPI and NHW with SIRs 5.11, 1.73 and 1.39 respectively (p < 0.05). NHAPI are at elevated risk for oral cavity/pharynx SPMs (SIR 2.19), esophagus SPMs (SIR 4.55) and SPMs in soft tissues including the heart (SIR 4.95) (all p < 0.05). NHB are more prone to gall bladder SPMs (SIR 4.34, p < 0.05). There is an elevated risk for biliary tract SPMs in NHW, NHAPI and H with SIRs 4.56, 4.17 and 7.53 respectively (p < 0.05). Pancreatic SPMs are also more likely in these groups with SIRs (p < 0.05) 2.14 in NHW, 2.47 in NHAPI and 2.53 in H. NHW are at elevated risk for melanomas (SIR 1.32, p < 0.05), Acute myeloid leukemia (SIR 1.79, p < 0.05) and Chronic Myeloid Leukemia (SIR 2.02, p < 0.05). NHAPI and H survivors are at higher risk for Non Hodgkin Lymphoma with SIRs 2.03 and 2.09 respectively (p < 0.05). Conclusions: EOCRC has seen a worrisome rise in recent years, and survivors face an elevated risk for several SPMs. This highlights the critical need for comprehensive survivorship care, including regular screening, tailored surveillance strategies, and preventive interventions, to address their unique long-term health risks and improve overall outcomes. SPMs in EOCRC survivors of different races/ethnicities. Site specific SIRs (p<0.05) NHW NHB NHAPI H Stomach 1.71 3.04 2.22 5.57 Small Intestine 10.6 8.26 8.71 12.42 Urinary bladder 2.22 2.58 3.75 1.95 Thyroid 2.16 1.92 3.51 2.77