Estimation of Potential Excess Cancer Incidence in Pediatric ²⁰¹Tl Imaging

Abstract

OBJECTIVE Little information is available regarding doses of ionizing radiation from medical imaging in the growing population of children undergoing therapy for cancer who are at risk of developing second cancers. The purpose of our study was to estimate the potential excess lifetime cancer incidence and mortality associated with thallium bone imging in pediatric patients. MATERIALS AND METHODS We retrospectively reviewed the medical records of pediatric patients treated between August 1991 and December 2003 for newly diagnosed osteosarcoma who underwent 201Tl imaging as part of the treatment protocol. According to age at diagnosis and doses of 201Tl, we estimated the excess cancer incidence and cancer mortality for boys and girls at 5 and 15 years old. RESULTS The study cohort consisted of 73 patients, 32 males (median age at diagnosis, 14.8 years; age range, 8.1–20.1 years) and 41 females (median age at diagnosis, 13.3 years; age range, 6.0–20.7 years). Patients underwent a total of three 201Tl studies with a median dose of 4.4 mCi (162.8 MBq) (range, 2.2–8.4 mCi [81.4–310.8 MBq]) per study. Total median cumulative patient radiation dose for 201Tl studies was 18.6 rem (186 mSv) (range, 8.4–44.2 rem [84–442 mSv]) for males and 21.5 rem (215 mSv) (range, 7.0–43.8 rem [70–438 mSv]) for females. Estimated excess cancer incidence was 6.0 per 100 (male) and 13.0 per 100 (female) if exposed by 5 years of age; 2.0 per 100 (male) and 3.1 per 100 (female) by 15 years of age. Estimated excess cancer mortality was 3.0 per 100 for males and 5.2 per 100 for females at 5 years of age; 1.0 per 100 (male) and 1.4 per 100 (female) exposed at 15 years of age. CONCLUSION Further reduction of doses in younger patients is needed to consider 201Tl a viable option for imaging osteosarcoma.

Cancer-Prone Mice Expressing the Ki-rasG12CGene Show Increased Lung Carcinogenesis after CT Screening Exposures

“…4). This observation is consistent with other data showing that females are often more radiosensitive than males (2, 4, 29, 30). …”

Impact of Socioeconomic Status on Ionizing Radiation Exposure From Medical Imaging in Children

“…Exposure to ionizing radiation at levels from diagnostic testing is associated with an increased risk of forming solid tumors, and that this risk is particularly notable in young children and those with cancer [39]. This study confirms previous work showing that patients of lower SES have greater disease burden.…”

“…Thus we agree that physicians caring for such patients must seek to limit radiation exposure whenever possible to lessen the lifetime risk of malignancy [38]. In children ages 5 to 21 diagnosed with osteosarcoma, excess cancer incidence and excess mortality decreased dramatically with age, with rates for 15 to 21 year olds 15% or less of values for children 5 to 10 [39]. For the 34 children in our sample diagnosed with metastatic solid tumors or lymphoma as well as for children with other diagnoses, we agree with the need to minimize patient exposure to ionizing radiation associated with medical imaging, with specific attention paid to young children, in considering the advantages of such imaging.…”