Induction of malignant bone tumors in radium-224 patients: Risk estimates based on the improved dosimetry

Mainly between 1945 and 1955, several thousand German patients with ankylos ing spondylitis, tuberculosis, or-in a few cases-other diseases received mu ltiple injections of the short-lived alpha-particle emitter radium-224, In the early 1950s, the follow-up of 899 patients was initiated, and the study has continued since then, It includes most of the high-dose patients and n early all of those treated as children or juveniles, i.e. under the age of 21, In the study cohort, 56 malignant bone tumors occurred in a temporal wa ve that peaked 8 years after exposure, whereas less than one case would hav e been expected during the follow-up, Most of the malignant bone tumors wer e osteosarcomas and fibrous-histiocytic sarcomas, A new analysis has now be en performed, primarily because an improved dosimetry resulted in modified bone surface doses, especially for those treated at younger ages. A signifi cant increase in bone tumor risk with decreasing age at exposure is now dem onstrated. The earlier finding of an inverse protraction factor is confirme d. In the new formulation, the dependence on dose rate or duration applies only at higher doses; i.e., the initial slope of the dose dependence is unr elated to dose rate or exposure duration, which is in contrast to earlier a nalyses but is in agreement with microdosimetric considerations and general radiobiological experience. (C) 2000 by Radiation Research Society.