AJR: Excess cancer incidence associated with pediatric thallium bone imaging
Further reduction of doses in younger patients is needed to consider Tl-201 a viable option for imaging osteosarcoma, according to research published in the January issue of the American Journal of Roentgenology.

The purpose of our study was to estimate the potential excess lifetime cancer incidence and mortality associated with thallium bone imaging in pediatric patients, wrote Najat C. Daw, MD, associate professor of pediatrics, University of Tennessee School of Health Science Center in Memphis.

Daw and colleagues retrospectively reviewed the medical records of pediatric patients treated between August 1991 and December 2003 for newly diagnosed osteosarcoma who underwent Tl-201 imaging as part of the treatment protocol.

“According to age at diagnosis and doses of Tl-201, we estimated the excess cancer incidence and cancer mortality for boys and girls at five and 15 years old,” said the researchers.

The study cohort consisted of 73 patients, 32 males (median age, 14.8 years) and 41 females (median age, 13.3 years) who underwent a total of three Tl-201 studies with a median dose of 4.4 mCi (162.8 MBq) per study.

Total median cumulative patient radiation dose for Tl-201 studies was 18.6 rem (186 mSv) for males and 21.5 rem (215 mSv) for females, wrote Daw and colleagues. 

“Estimated excess cancer incidence was six per 100 (male) and 13 per 100 (female) if exposed by five years of age; two per 100 (male) and three per 100 (female) by 15 years of age,” according to the authors.

Daw and colleagues also estimated the excess cancer mortality as three per 100 at five years of age and one per 100 at 15 years of age for males and five per 100 at five years of age and one per 100 exposed at 15 years of age for females.