Mortality from Cancer and Other Causes after Radiotherapy for Ankylosing Spondylitis

Abstract

A total of 14,554 patients with ankylosing spondylitis, who were treated with x rays during the period 1935–54, have been studied. More than 98% were traced on or after 1 January 1960, and less complete follow-up information is available for a further three years. The effects of irradiation have been assessed by comparing the numbers of deaths observed with the numbers that would have been expected if the patients had suffered the death rates recorded in the population of England and Wales as a whole. The most important finding, apart from the previously reported excess of deaths from leukaemia and aplastic anaemia, relates to other cancers originating in heavily irradiated tissues. Deaths attributed to these cancers were increased approximately twofold six or more years after first treatment, and 15 years after first treatment the excess showed no sign of diminishing. The excess was not limited to one or two types of cancer, but many different types contributed to it, approximately in proportion to their normal incidence. In contrast to these findings the number of deaths from cancers originating in lightly irradiated tissues was not increased significantly. It is estimated that in an average follow-up period of 13 years after first treatment the excess deaths from leukaemia and from other cancers arising in heavily irradiated tissues, which can be attributed to the effects of ionizing radiations, were 4 per 1,000 patients and 6 per 1,000 patients respectively. Deaths ascribed to spondylitis or rheumatism or to the direct complications of spondylitis were increased, as were to a less extent deaths due to a variety of other causes. Many different factors probably contributed to this, but their importance cannot be finally evaluated until results are obtained from a similar study of spondylitic patients treated by other means. We would like again to accord our gratitude to the directors and staffs of the 87 British radiotherapy departments who co-operated in this study. We are also greatly indebted to Miss F. Callaby, Miss A. Fotheringham, and Miss K. Jones for the arduous work of following up so many of the patients ; to Miss F. Callaby and to Mr. K. Bajaj for assistance in the analysis of the results ; and to Miss M. Devine, of the Medical Research Council's Computer Services Group, who prepared programmes for the most laborious calculations to be carried out on computers. © 1965, British Medical Journal Publishing Group. All rights reserved.