Radiation Therapy

Using X-rays and radioactivity to destroy cancerous cells

Soon after his 1896 discovery of radioactivity, Henri Becquerel noticed that the small amount of radium he always carried in his jacket pocket was causing a rash on his skin. In 1901, under similar circumstances, his colleague Pierre Curie noticed an identical rash appearing on his arm. Instances such as these prompted a sudden interest in possible medical uses of radioactivity – specifically as a tool to help treat tumours. After Pierre’s death, Marie Curie and Claudius Régaud combined physics, chemistry and medicine to become pioneers in a completely new kind of therapy.

Despite their enormous importance in the field, the Curie were not the first to venture into the medical applications of radiations: the first use of X-rays in medicine came only weeks after their original discovery in 1895. As soon as 1901, Dr Danlos of the Saint Louis hospital in Paris was already using exposure to radium to help treat a variety of skin problems.

Radiotherapy in 1925
The installation of a radiotherapy apparatus in Italy in 1925. The young man on the bed will be subjected to X-rays coming from the machine to the left of the picture to cure tinea on his head. As can be seen, the X-rays will be spread throughout the entire room, with virtually no precautions being taken. At that time, there were no techniques available to localise the incoming rays.
Institut Curie

Since then, hundreds of thousands of cancers have been treated by exposure to radium and its successors: iridium 192 and caesium 137. The radiation emitted by these particular isotopes has proven useful in treating a host of different diseases.

In only one hundred years, radiation therapy (using virtually all types of radiations) has developed into a highly sophisticated medical technique. Used in 50% of all cancer treatments, it has the ability to integrate seamlessly into current procedures, and is used side-by-side with surgery and chemotherapy.

Modern radiation therapy
This piece of apparatus shows the long way radiotherapy has come. This linear accelerator shows the latest model of technical equipment being used – a model that is gradually replacing the old cobalt 60-based treatment in most hospitals. The great advantage of these machines is their ability to direct the beams with higher degrees of accuracy.

In a developed country like France, over a hundred thousand cancer patients a year receive radiation therapy. Nowadays, gamma rays have replaced X-Rays. Beams of gamma rays are generated by small accelerators, that allows to direct them more accurately on tumors.

The impressive advances made over the past century have allowed for the emergence of so-called ‘conformal therapy: a procedure which is able to target the affected areas with ever-increasing accuracy. Using complex 3-D scans of the tumour and the surrounding organs, the incoming radiation can be adapted to fit the exact shape and size of the growth, thereby minimizing the dose absorbed by healthy cells. Such procedures have gone a long way to reducing the risks posed by radiation therapy.

Proton therapy for melanoma of the eye
Treatment for melanoma of the eye in the Orsay Proton Therapy Centre. The ‘beams’ of particles (protons, in this case) are used as a replacement for radioactive sources in a variety of radiation treatments. When dealing with a uveal melanoma (the name for tumours found in the retina), it is crucial to avoid unnecessarily exposing the brain – mere millimetres away – to radiation. Consequently, the higher-precision proton beams are preferred.
Centre de Protonthérapie d'Orsay

Brachytherapies are a much less frequent kind of therapies. Brachytherapies were first proposed by Marie Curie with radium needles.The principle is to fix radioelements. on or near a tumor. The radioeléments should emit beta rays or low energy gamma rays with a rangeof a few centimeters. They should also have a short lifetime and disappear after a few weeks or months. Examples are the treatment of hyperthyroidism and thyroid cancers by iodine-131 and brachytherapies of prostate using iodine-125 or palladium-123.

More rarely, particle beams provided by an accelerator are used to bombard malignant tissues. These therapies are called hadrotherapies or proton therapies in case of protons. The beam energy is tune so that the particles stop in these tissues where they cause maximum damage. For instance, proton therapies are used today in the treatment of eye melanoma.

An effective therapy relies on the application of appropriate doses and the ability to follow a patient’s progress after the exposure. Improved detection capabilities and larger data storage facilities have contributed to making radiotherapy an indispensable part of our response to cancer.

It must not be forgotten also that radiation treatment carries exposure-related risks: risks that doctors and radiologists have learnt to control. and limit.

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