Estimated radiation exposure and cancer risk from CT and PET/CT scans in patients with lymphoma.

INTRODUCTION

The purpose of this study was to estimate total effective dose and cancer risk related to treatment monitoring and surveillance computed tomography (CT) scans in a cohort of patients diagnosed with lymphoma.

METHODS

76 patients with head, neck, chest, abdomen or pelvis CT and whole-body positron emission tomography (PET)/CT were identified from an institutional lymphoma database; this included 54 (71%) patients with non-Hodgkin and 22 (29%) patients with classical Hodgkin lymphoma. Average treatment and surveillance periods were 8 months (range, 3-14 mo) and 23 months (range, 1-40 mo), respectively. Radiation exposure was estimated from the dose-length product (DLP) for CT scans and milli-Curies and DLP for PET/CT scans. Cancer risk was estimated using the Biological Effects of Ionizing Radiation model.

RESULTS

During their treatment period, 45 patients had 161 CT exams and 39 patients had 73 PET/CT exams. Mean effective dose was 39.3 mSv (range, 7.1-100 mSv). During the surveillance period, 60 patients had 378 CT exams and 25 patients had 39 PET/CT exams. Mean effective dose was 53.2 mSv (range, 2.6-154 mSv). Seventeen of 76 (22.4%) patients had total cumulative doses greater than 100 mSv. The mean increase in estimated cancer risk was 0.40%; the greatest estimated risk to any one patient was 1.19%.

CONCLUSION

Mean total effective dose and mean estimated cancer risk were low in patients with lymphoma undergoing serial imaging, suggesting that theoretical risks of radiation-induced cancer need not be a major consideration in radiologic follow-up.