The Evolution of Therapeutic Radiology
Very shortly after the European discovery of X-rays and radium in 1895 and 1898, scientists observed the effects of hair loss and skin damage from their rays. Both agents were then tried experimentally to treat superficial skin diseases and unwanted hair. X-rays quickly found use by physicians for diagnosing broken bones and locating foreign bodies (e.g. bullets). Radium appeared to have no other practical value until it was used to make luminous paint for time pieces and military vehicles in World War I.
By 1913 radium was being mined in America and General Electric advanced beyond gas tubes to create a 140 KV tube. Physicians advanced from skin cancer to treating other superficial cancers like breast, head, and neck lymph nodes. Scarce and costly radium was used in small tubes for insertion directly into cancers or into body cavities containing cancer. Inoperable cervical cancer became curable with radium. Beginning in 1922, GE began to develop special X-ray tubes with high energy (200 KV) for deep seated lung, abdominal and pelvic tumors. Shortly afterward, inoperable larynx cancer became curable.
Between World War I and II, physicists and biologists continued to discover how radiation works and how to measure the dose accurately. Physicists, electrical engineers, mining companies and commercial vendors continued to develop and market higher energy X-ray machines (one MV by 1937) and new radium devices. In America, surgery continued to be the foremost cancer therapy with irradiation reserved for inoperable, unresectable or recurrent tumors – thus radiation therapy (also called radiotherapy) gained notoriety as the "last hope".
Cyclotrons and nuclear reactors became available after World War II to produce synthetic radium and other radioactive elements for cancer treatment. The cobalt machine, using synthetic radium (1.2 MV), appeared in 1951 and 1,120 machines were sold to hospitals everywhere in the first 10 years. Radar research led to the creation of the medical linear accelerator X-ray machine in 1953. These "linacs" quickly went from 4 MV energy to 18 MV and began to dominate the market. Improved cure rates followed the introduction of first the cobalt and then the high-energy linacs. Hodgkin’s lymphomas and testicle cancers became curable.
In the 1970s, computers were introduced into treatment planning. Radiology developed CAT, MRI and PET scans so that tumors could be targeted with precision. This was followed by intensity modulated and image guided radiation therapy (IMRT and IGRT) machinery which could use these new diagnostic advances to now deliver the dose with pin-point accuracy while avoiding normal tissues. These radiology advances have been joined by those in surgical and medical oncology so that organ preservation in now probable in cancers of the prostate, breast, cervix, anus, larynx and esophagus. Using this new team approach in oncology will continue to increase the number of cured patients with minimal side effects.
-- Roger F. Robison, MD, Bloomington, Ind.
More information on the history of radiation therapy is available on the ASTRO website.