Abstract 7449: Incidence of secondary malignancies in early onset colorectal cancer (EOCRC) patients
Authors: Vadehra Deepak , Attwood Kristopher , George Anthony , Advani Shailesh , Sonti Sahithi , Mukherjee Sarbajit 
Published: March 2024

Introduction: The incidence of colorectal cancer in the younger population (20-49) continues to rise at a rapid pace. EOCRC patients are potentially at risk for developing additional secondary malignancies. There is a lack of reported data in the EOCRC space. In this analysis, we seek to examine the incidence, trends, and outcomes of secondary malignancies in EOCRC patients.

Methods: The surveillance, epidemiology, and end-result (SEER) database was utilized to assess and compare the incidence and factors associated with development of secondary malignancies among EOCRC patients. Patient characteristics were summarized by secondary cancer status and compared using the Pearson chi-square test. Further OS was assessed using Kaplan- -Meier methods and compared across groups using the log-rank test. Multivariable Logistic regression models using backward selection approach were used to evaluate the association between patient characteristics and risk of secondary cancers. All statistics were performed using SAS version 9.4 (SAS Institute Inc., Cary, NC).

Results: Of the 53,891 patients analyzed, 2578 (4.8%) patients with EOCRC developed a secondary malignancy in the SEER database from 2000-2019. The mean age for developing a secondary malignancy was 47.6 yo (median 48 yo; range 20-69). There was a higher likelihood of second cancers among men(56%), white patients (61.4%), those with stage II (25.5%). and III (32.8%) CRC. The patients who most commonly developed a secondary malignancy were in the age group 40-49(p &lt;.001). Of the patients who developed a secondary malignancy, 1843 (71.5%) initially had a primary colon cancer compared to 920 (22.6%) having rectal cancer, with the remainder having a rectosigmoid cancer. Of the patients who developed secondary malignancies, a majority had received prior chemotherapy (58.5%), and a minority of patients received radiation therapy (20.6%) Patients who had a partner had a higher incidence of secondary malignancy (59.5%) and they were more likely to have resided in a metropolitan area compared to a nonmetropolitan area (86.6 versus 13.2% respectively). The most common sites of secondary malignancy were: an additional colorectal cancer (47.7%), followed by breast cancer (8.2%) urinary tract cancer (7.1%), thyroid cancer (7%) and prostate cancer (5%). Patients who developed a secondary cancer were found to have an improved disease specific survival (DSS) compared to those who did not develop a secondary malignancy (3 year mDSS 89% vs 74%; p &lt;.001)The overall survival of patients who developed a secondary malignancy was worse than those who did not develop one (mOS 208 months vs 229 mos respectively).

Conclusion: EOCRC patients are likely to develop secondary malignancies. Long-term screening should be recommended for these patients and integrated into their survivorship plans.

Citation Format: Deepak Vadehra, Kristopher Attwood, Anthony George, Shailesh Advani, Sahithi Sonti, Sarbajit Mukherjee. Incidence of secondary malignancies in early onset colorectal cancer (EOCRC) patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 7449.