The cancer burden in the United Kingdom in 2007 due to radiotherapy

Abstract

The number of long-term cancer survivors in the general population of the UK is substantial and increasing rapidly. Many cancer survivors have been treated with radiotherapy but the likely number of radiotherapy-related second cancers has not previously been estimated. We used estimates of the numbers of cancer survivors in the UK at the beginning of 2007, in conjunction with estimates of the relative risk of a second primary cancer associated with previous radiotherapy from the United States Surveillance Epidemiology and End Results (SEER) programme, to estimate the numbers of incident cancers in the UK in 2007 that were associated with radiotherapy for a previous cancer and that may have been caused by it. We estimated that 1,346 cases of cancer, or about 0.45% of the 298,000 new cancers registered in the UK in 2007, were associated with radiotherapy for a previous cancer. The largest numbers of radiotherapy-related second cancers were lung cancer (23.7% of the total), oesophageal cancer (13.3%), and female breast cancer (10.6%); 54% of radiotherapy-related second cancers were in individuals aged 75 or over. The highest percentages of second cancers related to radiotherapy were among survivors of Hodgkin's disease and cancers of the oral cavity and pharynx and cervix uteri; over 15% of second cancers among these survivors were associated with radiotherapy for the first cancer. These calculations, which involve a number of assumptions and approximations, provide a reasonable, if conservative, estimate of the fraction of incident cancers in the UK that are attributable to past radiation therapy.Around 3% of the UK population are cancer survivors, with the total number now around two million and increasing by 3% per annum. 1 The increasing trend is partly the consequence of an ageing population but also the result of the successful use of several types of therapy, including radiotherapy. For many cancers, treatment with radiotherapy involves some incidental irradiation of the surrounding normal tissues, thus increasing the risk of a radiation-induced second cancer. Up until now, estimates of the radiation exposure of the UK population have not included exposure from radiotherapy, 2,3 and the total number of cancers in the UK population associated with past radiation exposure from radiotherapy has not previously been assessed.The largest study evaluating the risk of second cancers is the follow-up of more than two million cancer cases registered within the United States Surveillance Epidemiology and End Results (SEER) programme from 1973-2000, 390,000 of whom had survived 10 years or more. 4 That study provides, for several cancer sites, the risk of developing a second primary cancer at varying intervals after diagnosis of the initial cancer in individuals who have, and who have not, received radiotherapy. We used the SEER data, in conjunction with estimates of the numbers of survivors of different cancers in the UK at the beginning of 2007, to estimate the number of incident cancers in the UK during 2007 that wer...

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