RADIATION DOSIMETRY IN A COHORT STUDY.

The cohort study in question is, "E2C Second Cancers After a First Cancer in Childhood: A Cohort Study. ", carried out by a group of the Unite de Recherche en Epidemiologic des Cancers, Institut National de la Sante et de la Recherche Medicale and the Institut Gustave Roussy.

The understanding of dose response relationships and consequently derived risk factors arose intially from studies of Japanese A-bomb victims and have been extended by various epidemiological studies. To further understand the effects of ionising radiation on man, children who have received radiation for the treatment of a cancer are an interesting group to follow for various reasons. Firstly due to the possible long natural duration of follow-up necessary to detect second tumours, which may develop forty years or more after an irradiation. Secondly, the group is already "biasfree" in that all the members have shown a certain predisposition to develop a cancer. Lastly and very importantly in a study looking at dose-response relationships is that accurate records are available in the form of treatment sheets, calculations and simulation and verification X-ray films. With medical irradiation treatment conditions and doses are accurately calculated to the treatment volume, leaving the possibility of calculating the lower doses recieved outside the treated volume.