Correlation of Cumulative Diagnostic Radiation Exposure With Increasing Lemann Index: The Need for Increased Provider Vigilance in Certain Crohnʼs Disease Sub-groups

Abstract

Introduction: Recurrent exposure to diagnostic ionizing radiation and the resultant increase in lifetime risk of cancer is a well-known concern in Crohn's disease (CD) patients. Lemann Index (LI) is a new metric that quantifies bowel damage mediated by CD. Stratification of CD patients based on change in LI over time is a novel approach to defining patient subgroups. We aimed to evaluate ionizing radiation exposure secondary to diagnostic testing, across different CD trajectories in a cohort stratified by change in LI. Methods: CD patients with 5 year(y) follow-up from a registry maintained at a tertiary center were included. LI was calculated using a computerized model from first (LI1) and last (LI2) clinical encounters. Patients were stratified based on change in index (LI2-LI1) or the delta LI (DLI) as showing improvement, no change or deterioration. Subgroups were created by dichotomizing mean improvement, mean deterioration and no change and used for association analysis with the cumulative effective dose (CED) of radiation received during 5y. Results: A total of 363 CD patients with 5y complete follow-up formed the study cohort [median age 43y (IQR: 33.3-55); 57% female; median disease duration 12y (IQR: 3-19), overall surgical exposure 69.7%]. Median (IQR) LI1, LI2 and DLI were 8 (0-54), 9 (0-75) and 0 (-22 - 47) respectively. Patients were stratified based on DLI into subgroups (A: DLI < -2.98; B: DLI -2.98 - 0; C: DLI 0, D: DLI 0 - 7.75; E: DLI >7.75). The study cohort underwent a total of 1414 diagnostic tests associated with radiation exposure (including abdominal radiographs, computed tomography [CT] scans and barium studies) with a median CED of 20mSv/person and median yearly radiation exposure of 4mSv/person/y. Use of CT scans accounted for 93.5% of CED. There was a significant difference in the number of tests and CED across the subgroups (p < 0.001), with highest and least median CED noted in groups E and C respectively [Table 1]. CED showed significant correlation with DLI (r = 0.35; p < 0.001).Table 1: Differences in cumulative effective dose of radiation received amongst Delta Lémann Index based five year trajectories of Crohn's diseaseConclusion: Identifiable subsets of patients with Crohn's disease are at risk of exposure to significant amounts of diagnostic radiation. When compared with natural background radiation exposure (3.1mSv/y), patients with rapidly worsening LI are exposed to 4 times higher dose of ionizing radiation each year. Clinicians must remain vigilant of the risk of cumulative radiation, particularly in patients with aggressive disease.