Lessons from history #7: medically induced thyroid cancers

In the 1940s to 1960s, children with an upper respiratory illness were often thought to have an enlarged thymus gland (in the neck), and were given some radiation therapy to settle it down. The thymus shrank after being irradiated and the kids generally got better, so the practice continued. It didn't matter that this was not a real disease, or that the treatment was not appropriate, or that the kids would have improved anyway; doctors did something and the patients got better. That, and some cockamamie biological explanation, was all the doctors needed. Well, that and some insurance to cover the medical costs of the kids who got cancer as a result of the radiation.

This study followed up children who had been irradiated for an enlarged thymus in the 50s, about 40 years later. The increase in thyroid cancers was present for all groups, right down to the lowest doses. The rate remained higher than expected nearly 60 years later as reported by this study.

Unfortunately, radiation was given for many more conditions around the head and neck of children, including enlarged tonsils and scalp conditions such as tinea. The thyroid gland is known to develop cancer after exposure to ionising radiation, particularly in children, where the risk gets higher, the younger they are. This study summarises the risks for children, and shows that the risk of developing thyroid cancer after exposure exists even for very low doses of radiation, and the risk remains elevated even at 40 years from the time of exposure.

It is well known that radiation treatment for cancer can cause later, different cancers (like leukaemia and lung cancer), but in those cases, it is likely that the benefits of the radiation outweigh the risk of later cancer. My problem with the cancers caused from irradiating children with benign conditions is with the decision making process. The patients in these cases either had conditions that were self-limiting, treatable by other means, or non-existent (‘enlarged thymus’). Not only was the thymus probably not enlarged (it is normally larger in children), it didn’t cause any of the conditions it was blamed for (such as asthma and sudden infant death). This didn’t stop some doctors at the time suggesting that chest radiation therapy be given to all newborn children (the next time some says that “prevention is better than cure”, think twice). Click here for a historical overview.

The bottom line

The decision to use radiation therapy for benign conditions in children is about as good an example of overestimating the benefits and underestimating the harms as you can get, and with all the hallmarks of bad treatment that we see today: confirmation bias, the false attribution of cause and effect, herd instinct and a general lack of application of scientific principles.