Radiation therapy
In 1895, Wilhelm Röntgen discovered X-rays, a moment that would eventually birth the field of radiation therapy. Emil Grubbe of Chicago became possibly the first American physician to use these rays to treat cancer in 1896. Before the 1920s, the hazards of radiation exposure were not understood, and little protection was used. Radium was believed to have wide curative powers, and radiotherapy was applied to many diseases beyond cancer. The early days saw radium, its emanation known as radon gas, and the X-ray tube serving as the only practical sources for treatment. External beam radiotherapy began at the turn of the century with relatively low voltage machines under 150 kilovolts. These early devices could treat superficial tumors but required higher voltages to reach deeper cancers inside the body.
Radiation therapy works by damaging the DNA of cancer cells, causing them to undergo mitotic catastrophe. This damage occurs through direct ionization or indirect ionization via free radicals formed from water molecules. Indirect ionization creates hydroxyl radicals that then attack the DNA chain. Cancer cells generally reproduce more than healthy differentiated cells and possess a diminished ability to repair sub-lethal damage. Single-strand DNA damage passes on through cell division until it accumulates enough to cause death or slow reproduction. Double-stranded breaks are much harder to repair and lead to dramatic chromosomal abnormalities. Solid tumors often become deficient in oxygen, creating a state called hypoxia. Cells in this environment can be two to three times more resistant to radiation damage than those in normal oxygen environments.
Megavoltage X-ray units were first built in the late 1930s but cost limited their use to few institutions. One early unit installed at St. Bartholomew's hospital in London in 1937 used a 30-foot long X-ray tube and weighed 10 tons. The invention of the nuclear reactor during World War 2 made artificial radioisotopes possible for treatment. Cobalt-60 teletherapy machines revolutionized the field between the 1950s and the early 1980s. These machines were relatively cheap and robust but required replacement every five years due to a half-life of 5.27 years. Medical linear particle accelerators developed since the 1940s began replacing older units in the 1980s. The first medical linear accelerator was used at Hammersmith Hospital in London in 1953. Godfrey Hounsfield invented computed tomography in 1971, allowing three-dimensional planning to become a possibility.
Intensity-modulated radiation therapy allows computer-controlled X-ray accelerators to distribute precise doses to malignant tumors. This technique improves the ability to conform treatment volume to concave tumor shapes wrapped around vulnerable structures. Volumetric modulated arc therapy introduced in 2007 delivers radiation by rotating gantry fields up to 360 degrees. Stereotactic body radiation therapy treats subcranial lesions with large doses per fraction ranging from 2.2 to 20 Gy. Brachytherapy places radioactive sources directly inside or next to the cancerous tumor to minimize exposure to healthy tissue. Radionuclide therapy uses isotopes like iodine-131 for thyroid cancer or lutetium-177 for neuroendocrine tumors. The FDA approved Lutathera for pediatric patients aged 12 or older with somatostatin receptor-positive gastroenteropancreatic neuroendocrine tumours in April 2024.
Common questions
When did Wilhelm Röntgen discover X-rays and how did it lead to radiation therapy?
Wilhelm Röntgen discovered X-rays in 1895, which eventually birthed the field of radiation therapy. Emil Grubbe of Chicago became possibly the first American physician to use these rays to treat cancer in 1896.
How does radiation therapy damage cancer cells at a cellular level?
Radiation therapy works by damaging the DNA of cancer cells through direct ionization or indirect ionization via free radicals formed from water molecules. This process creates hydroxyl radicals that attack the DNA chain leading to mitotic catastrophe and cell death.
What were the characteristics of early megavoltage X-ray units built in the late 1930s?
Megavoltage X-ray units were first built in the late 1930s but cost limited their use to few institutions. One early unit installed at St. Bartholomew's hospital in London in 1937 used a 30-foot long X-ray tube and weighed 10 tons.
Which medical linear particle accelerators replaced older units and when was the first one used?
Medical linear particle accelerators developed since the 1940s began replacing older units in the 1980s. The first medical linear accelerator was used at Hammersmith Hospital in London in 1953.
When did the FDA approve Lutathera for pediatric patients with specific neuroendocrine tumours?
The FDA approved Lutathera for pediatric patients aged 12 or older with somatostatin receptor-positive gastroenteropancreatic neuroendocrine tumours in April 2024. This drug uses isotopes like lutetium-177 for treating such tumors.