radiotherapy

radiotherapy refers to the use of ionizing radiation in the treatment of disease — mainly cancer.

Radiation — exposure to X-rays or gamma rays — can kill cells or stop their growth. It can be effective in the treatment of cancerous growths, because malignant cells are more sensitive than normal body cells: the radiation can be applied to a particular area, whilst the rest of the body is shielded from it.

Historically, radiotherapy dates back to the discovery of X-rays by Röntgen in 1895, and of the radioactivity of substances such as uranium by Becquerel in 1896, leading to that of radium, identified in 1898 by Marie and Pierre Curie.

The first use of X-rays as a treatment, for breast cancer, occurred in the USA within two to three months of their discovery. More followed within a year in Germany, France, and Austria. The loss of hair which followed exposure in these early cases alerted the medical profession to potentially harmful effects on normal tissues. The first report of successful treatment by X-ray was of a skin cancer in 1899. The use of radium in treatment was explored after Becquerel had been burnt by carrying a tube of radium in his pocket. The first accredited success, again for skin cancer, was in 1903. Radium tubes could be inserted, for example for treatment of uterine cancer (the standard method in the 1930s), or rays from a radium source could be directed at the lesion. Radium ‘needles’ were also inserted into tumours such as breast cancers. ‘Teletherapy’ — directing beams of radiation at the appropriate part — was thus a method applicable to either X-rays or radium. The two continued to be the mainstay of cancer treatment for the first half of the twentieth century.

Despite early realization of danger, protection of personnel involved in radiotherapy was not taken seriously before the mid 1930s nor implemented adequately until considerably later than that. In the late 1920s it was even recommended that the physician should use the redness produced on his own skin to determine the appropriate X-ray dose for a patient.

The discovery of plutonium-239 in 1941 led to the therapeutic use of artificially produced radioactive isotopes (as well as to nuclear weapons). The gamma rays which these emit can be directed at a tumour through a tube or needle. They are safer than X-rays both for patients and attendants; they have a much shorter half life than radium and emit gamma rays of lower energy. Thus cobalt-60 for example mainly supplanted radium for cancer of the uterus, and other radioisotopes, such as caesium-137 and iridium-192, have been developed for particular uses. These treatments, along with the diagnostic imaging techniques which employ radioisotopes have become the province of the specialty of nuclear medicine.

X-rays, however, have not been supplanted. In recent years radiologists involved in radiotherapy have expanded their activities to include the use of radioisotopes and also the combination of radiotherapy with a variety of chemotherapeutic drugs or with hormones in the treatment of cancer. This specialty is now termed, ‘radiation oncology’.

J. K. Davidson

See also cancer; chemotherapy; imaging techniques; radiation, ionizing; radioactivity; radiology; X-rays.