Trends of gastrointestinal secondary primary malignancy in chronic lymphocytic leukemia patients from 2000-2021: Surveillance, Epidemiology, and End Results (SEER) database.

e15698 Background: Chronic lymphocytic leukemia (CLL), the most common leukemia in the U.S. and among elderly populations, has an incidence of 4.9 per 100,000 and a prevalence exceeding 200,000. Advances in treatment have raised the 5-year survival rate to 87%. However, a key concern is the development of secondary primary malignancies (SPMs), driven by immune dysfunction, treatments, and shared risk factors, necessitating ongoing monitoring. Gastrointestinal (GI) SPMs significantly impact morbidity and survival, yet CLL patients lack specific screening guidelines, including colonoscopy, and instead follow recommendations for average-risk individuals.This study examines GI SPM trends in CLL patients from 2000 to 2021 using SEER data, aiming to highlight the need for dedicated screening protocols. Methods: The SEER registry (2000–2021) was analyzed to evaluate GI SPMs in CLL patients. Observed and expected cancer cases were used to calculate the Standardized Incidence Ratio (SIR), comparing SPM risk in CLL patients to the general population. Latency periods (2–11, 12–59, 60–119, ≥120 months) and study years (2000–2005, 2006–2010, 2011–2015, 2016–2021) were analyzed for temporal trends.SIR and timing of GI cancers were plotted to identify patterns over time, and only statistically significant data were included to ensure accuracy and relevance. Results: SPMs in CLL patients from 2000 to 2021 revealed distinct trends in SIR across GI cancer sites and latency periods, with increased risk in early latency (2–11 months post-diagnosis). Stomach cancer had a high SIR of 2.32 in 2000–2005 but declined over time. The small intestine recorded the highest SIR of 4.65 in 2006–2010, while the cecum showed an upward trend, peaking at 3.53 in 2016–2021. Medium latency (12–59 months) revealed rising risks in the ascending colon (SIR 1.99 in 2016–2021), and long latency (60–119 months) saw a spike in rectosigmoid junction cancers (SIR 2.71 in 2011–2015). Over time, the burden of GI cancers shifted from the stomach and small intestine to the cecum, ascending colon, and large intestine in recent years. Conclusions: The study reveals a shifting burden of secondary GI malignancies in CLL patients, with increasing risks in the cecum, ascending colon, and large intestine (NOS), particularly during early latency periods. These findings highlight the need for specific colorectal cancer screening guidelines tailored to CLL patients particularly in the early period after diagnosis, given the evolving cancer burden. Limitation includes lack of treatment details, reporting bias and unaccounted confounding factors warranting further prospective studies.