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* = Presenting author

P205 Ionizing radiation throughout the duration of immunosuppression therapy in Crohn's disease: should it remain a concern?

R. Coelho*1, F. Magro1, L. S. Guimarães2, M. Silva1, A. Peixoto1, S. Lopes1, G. Macedo1

1Centro Hospitalar São João, Gastrenterology, Porto, Portugal, 2Centro Hospitalar São João, Radiology, Porto., Portugal

Background

Crohn's disease (CD) patients undergo many radiological studies employing ionizing radiation for diagnosis and management purposes. Our aim was to assess the total radiation exposure of our patients over the years, to estimate risk factors for exposure to high doses and to correlate radiation exposure to immunosuppression.

Methods

The cumulative effective dose of radiation (CEDR) was calculated multiplying the number of imaging studies by the effective dose of each exam. Radiation dose data was collected prospectively.

Results

Four hundred and fifty-one patients with CD (226 female) were followed during 11.0 years (IQR: 6.0-16.0), with 52.1% of the patients being B3-classified patients and 38.6% being steroid dependent. Thirty nine percent of the patients were under combo therapy and 41% had previous abdominal surgery. Sixteen percent were exposed to high radiation dose levels (CEDR>50 mSv) and 4% to CEDR>100 mSv. The mean CEDR between 26-35 years old was 12.539 mSv and a significant dose of radiation (over 50 mSv) was achieved at a median age of 40 (IQR: 29.0-47.0).

Abdominal-pelvic computed tomography (CT) scan was the examination that contributed the most for CEDR.

High CEDR ( β value; 95% CI) were found for penetrating disease phenotype (22.785, 17.139;28.431), steroid resistance or dependence (8.860, 3.050;14.670), abdominal surgery (18.673, 13.217;24.129), azathioprine (14.739, 6.875; 22.603) and anti-TNF therapy (17.141, 11.564; 22.716). Patients with penetrating phenotype (B3), previous surgery, azathioprine and anti-TNF α therapy were exposed earlier on the course of the disease to CEDR above 50 mSv (p<0.001). The value of CEDR in the patients under immunosuppression mainly increased in the first year of immunosuppression.

ECCOJC jju027 P205 F0001

Conclusion

Penetrating phenotype, abdominal surgery, steroid resistance or steroid dependence and treatment with anti-TNF α and azathioprine were predictive factors for high CEDR. It was also demonstrated that immunosuppression and anti-TNF α treatment were followed by a sustained increment of radiation exposure.