P3659 - Secondary-Primary Colon and Rectal Cancer in Prostate Cancer Patients After Radiation Therapy

Akram Ahmad, MD¹, Zaid Ansari, MD², Osama Sherjeel Khan, MD¹, Ritu Channagiri, BS³, Ashraf Almomani, MD¹, Fernando NA. Castro, MD^1
1Cleveland Clinic Florida, Weston, FL; ²Cleveland Clinic Florida, Plantation, FL; ³Cleveland Clinic Florida, Boca Raton, FL

Introduction: Radiation therapy is one of the core treatment modalities for prostate cancer. The long-term impact of pelvic radiation therapy is debatable, but some studies suggested a modest increase in the risk of rectal cancer. We hypothesized that patients suffering from post-radiation proctitis are more prone to rectal cancer due to chronic mucosal and vascular damage.

Methods: This retrospective multicenter study examines patients with prostate cancer who received pelvic radiation therapy between January 2000 and December 2023. The study aims to compare the risk of colon and rectal cancer in patients who developed radiation proctitis with those who did not. Patient information was extracted from electronic medical records using validated ICD codes. Subjects were excluded if they had a history of colectomy, or colorectal cancer, or received radiation therapy for a different condition before their prostate cancer diagnosis.

Results: Among the 13,255 patients evaluated during the study period, 563 developed radiation proctitis. Within this group, 28 patients (4.97%) had colorectal cancer and 15 patients (2.66%) had rectal cancer. In contrast, among the patients who did not develop proctitis, 109 (0.86%) had colorectal cancer and 41 (0.32%) had rectal cancer (P < 0.01). Radiation proctitis was associated with an odds ratio of 8.45 for rectal cancer (4.65-15.35, P < 0.0001). There was no difference in family history of colon cancer, type, or dose of radiation therapy between the study groups (Table 1). However, more patients in the proctitis group had completed at least one colonoscopy before radiation therapy (Table 1).

Discussion: Although pelvic radiation therapy is associated with an increased risk of secondary primary tumors, the impact of radiation on the development of cancer has not been previously studied. We focused on a subgroup of patients who developed radiation proctitis and found that the rate and odds ratio of secondary primary rectal cancer is significantly higher compared to the general population who received pelvic radiation. However, this study is limited by its retrospective design and reliance on ICD codes to identify the target populations. Future larger and prospective studies are needed to validate our findings.


Disclosures:


Akram Ahmad, MD¹, Zaid Ansari, MD², Osama Sherjeel Khan, MD¹, Ritu Channagiri, BS³, Ashraf Almomani, MD¹, Fernando NA. Castro, MD¹. P3659 - Secondary-Primary Colon and Rectal Cancer in Prostate Cancer Patients After Radiation Therapy, ACG 2024 Annual Scientific Meeting Abstracts. Philadelphia, PA: American College of Gastroenterology.