Cancer is a disease that people have known about for centuries. It is even mentioned in the medical case studies of the ancient Egyptian physician Imhotep. Under potential treatments for the disease, he simply remarks “none”. Hippocrates found his patients’ tumors to be reminiscent of crabs burrowed in the sand, inspiring him to name the notorious disease ‘Karkinos’ – the Greek word for crab. Later, the more common term was the Latin translation of the word: cancer. But what is cancer, and how does it develop?
This question was first answered by Rudolf Virchow in the mid-19th century: Cancer is a disease that occurs when pathologically altered cells multiply in an uncontrolled manner. Cancer generally begins as a local disease, only later spreading to the rest of the body. Between these two phases is a window of opportunity during which the cancer can still be treated locally. For a long time, surgery was the only available option to this end.
The discovery of X-rays in 1895 revolutionized the field of medicine. Just three weeks after this breakthrough, the Hungarian pathologist Endre Högyes wrote: “There is no doubt that in addition to their chemical effect, the rays are also biologically active, and will one day play a therapeutic role in medicine.” And so, researchers fascinated by the new technology set about exploring its therapeutic potential. One of the first was the physician Leopold Freund. In 1896, he treated a girl suffering from abnormal back hair growth with X-rays at the Vienna General Hospital.
To begin with, no there were no dedicated devices for radiation therapy. The first major step in this direction was the X-ray tube developed by William Coolidge in 1913, which generated harder radiation able to penetrate further into the body. Building on this invention, Friedrich Dessauer, a pioneer of radiation therapy, went on to develop his Reform Apparatus. Meanwhile, Reiniger, Gebbert & Schall (RGS) in Erlangen also created a successful X-ray device designed specifically for deep therapy, the Symmetry Apparatus.
As radiotherapy sessions often lasted for hours at a time, radiation protection became a key focus – even more so than in diagnostic X-ray procedures. In 1922, the “Siemens Bestrahlungskasten” (irradiation box) became the first Siemens device to reliably protect operators and patients from the harmful effects of deep X-ray therapy, such as radiation, but also high electrical voltage. The development simplified treatment, while reducing the discomfort involved. Key components of the Bestrahlungskasten were the Stabilivolt and Multivolt systems, which were less prone to malfunctions and allowed shorter exposure times.
Depth and precision
Despite these major breakthroughs, in the early days of radiotherapy it was not possible to generate X-rays hard enough to successfully treat deep-seated tumors. A solution to this problem arrived in the form of circular accelerators, which used electromagnetic fields to accelerate electrons on a circular path before abruptly decelerating them, thereby generating very hard X-rays. In 1950, Siemens-Reiniger-Werke unveiled the Betatron circular accelerator at the International Congress of Radiology in London.
In the following decades, these devices were replaced by linear accelerators – such as the Siemens Mevatron. Accelerating electrons in a straight line resulted in superior output and radiation that was even better suited to cancer treatment. As a result, radiotherapy became established as the second pillar of cancer treatment alongside surgery. The third pillar – chemotherapy – followed in the 1950s.
With the linear accelerator, any tumor could be reached – no matter how deeply it was situated in the patient’s body. However, the tumor’s size and position could only be roughly estimated. With the emergence of computed tomography in the early 1970s, it became possible to determine tumor size and position exactly, allowing radiation dosage to be fine-tuned in relation to the tumor. Moreover, CT scans made it possible to observe how the radiation penetrated the body of each individual patient, allowing even more precise dose adjustment. Refinements in computed tomography (CT), combined with the development of magnetic resonance imaging (MRI), and above all positron emission tomography (PET) meant that tumors could be viewed in unprecedented detail, with all their ramifications, bulges, and indentations.
Exploiting these complex images required increasingly sophisticated tools, leading to the development in the 1990s of intensity modulated radiation therapy (IMRT), which offered a way to almost exactly recreate the contours of the tumor with X-rays. The result was a sculpture consisting of a large number of individual X-ray beam segments with different dose distributions that very closely approximates the shape of the actual tumor, allowing the radiation to be targeted with a very high degree of precision. The PRIMUS linear accelerator launched by Siemens in 1997 became one of the most successful accelerators to use the new IMRT technology.
However, the growing precision with which X-rays could be focused on the tumor made it all the more important to control the patient’s position during radiotherapy. To this end, hybrid systems combining linear accelerators and CT scanners were developed. In 2002, PRIMATOM became the first such hybrid system on the market, and image-guided radiotherapy emerged as the new standard. Meanwhile, given that tumors and their surrounding environment can also change during radiotherapy, there was a need for systems that could provide real-time monitoring and, where necessary, dosage adjustment during treatment. This was made possible by the ARTISTE system, launched in 2006, resulting in even more effective protection of the healthy surrounding tissue.
Prevention and risk
These developments notwithstanding, the prospects of successfully treating cancer still remain highest when the disease is detected at an early stage. Accordingly, preventive checkups and screenings play a crucial role. The most prominent screening program is mammography for women between the ages of 50 and 70. Siemens Healthineers has catered to this need with its Mammomat range since 1972. For one of the most common forms of cancer, lung cancer, a screening program for high-risk patients involving a low-dose CT scan is under discussion. SOMATOM go.Up, supports scan speed to allow lung cancer screening. Meanwhile, blood or tissue sample testing can increasingly be used to identify patients at greater risk of developing certain types of cancer, or medications that are more likely to be effective for a given patient. In future, the ability to combine laboratory and imaging data will enable clinicians to customize treatment to the individual patient with ever greater precision, as well as allowing constant monitoring of the treatment’s success.