Basic research brings hope to cancer patients
Tumour therapy that is effective in nine out of ten patients and causes side effects in only a few individual cases – that sounds almost utopian. Yet radiation therapy with carbon ions has been a reality since researchers at the GSI Helmholtz Centre for Heavy Ion Research and TU Darmstadt developed it in 1997. More than 440 patients with inoperable tumours in the head and neck area had been treated successfully by 2009.
During the first years, treatment was conducted in a therapy room on GSI premises. Since the end of 2009, the Heidelberg Ion-Beam Therapy Centre has been routinely treating an annual volume of more than 750 patients. Other therapy centres are being planned or constructed in Germany and around the world.
This therapy is so successful because carbon ion beams effectively destroy tumour cells whilst leaving the healthy tissue surrounding the tumour intact. The key to this is the way in which the ion beam is decelerated within the patient's body: ions, i.e. charged atoms, initially penetrate the body with hardly any loss of speed.
Surrounding tissue remains unharmed
Only on the last few millimetres of their trajectory will the ions be abruptly slowed down. In the process, virtually their entire energy is released into an area of tissue no larger than a pinhead, whilst putting hardly any stress on the rest of the body. The penetration depth of the beam can be controlled precisely by the speed of the ions. Magnets can be used to divert the beam sideways with such precision that the ion energy is only distributed across the tumour, destroying cancer cells whilst leaving the surrounding tissue unharmed.
When biophysicist Gerhard Kraft began developing Ion Beam Therapy in Darmstadt in the 1980s, it had been known for decades that ion beams irreparably damage the genetic make-up of cancer cells, thus killing them. In the US at the time, cancer patients were treated with neon ion beams. However, the American treatment consisted of shooting a thick bundle of neon ions onto the cancer, which also damaged healthy cells round about.
Gerhard Kraft, who also taught at TU Darmstadt, had another idea: in order to channel the ion energy exclusively into the tumour, he generated a pencil-thin ion beam in the GSI ion accelerator, which was actually used for basic research in physics, and directed it exactly over the three-dimensional shape of the tumour.
Ion Beam Therapy as a recognised medical treatment
Years of research ensued, which led to the conclusion that the atomic particles of carbon ions are best suited for therapy. Of all elements they had the strongest cytocidal effect on the tumour tissue and could be directed with sufficient precision. Lighter ions produced insufficient biological effects, whilst heavier ions killed cells before they even reached the tumour.
Finally, in 1997, the first patients were treated for tumours at the base of the skull, in the spine and the prostate in a separate room at GSI. The method quickly proved its effectiveness: depending on the type of tumour, its growth could be stopped in 75 to 90 percent of patients. Ion Beam Therapy was officially recognised as a treatment option – success that also owed much to close cooperation with the German Cancer Research Center and the Helmholtz-Zentrum Dresden-Rossendorf.
And research continues: GSI researchers under biophysicist Marco Durante, who teaches at TU Darmstadt, are currently working on a tracking system for the ion beam that will allow treatment of moving organs such as the lung.There is also hope that ion beams may be used in other areas of medicine.