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Patients survive incurable disease longer
Together with US colleagues researchers from the University of Bonn have developed a new treatment which enables certain types of cancer to be treated more effectively than was previously the case. The radioactive substance becomes particularly concentrated in metastases in the bones and partially destroys them. To date such metastases have been incurable. In repeated application of the new medication, however, some patients survive on average almost twice as long as in the past. What is more, the medication is almost without side effects. The researchers have now published their findings in the prestigious Journal of Clinical Oncology (August 2003, pp.2869-2875).
Bone metastases are formed when the bone marrow is flooded with tumour cells - e.g. of cancer of the prostate. There the cancer cells can proliferate uncontrollably as metastases, thereby also destroying the bone trabeculae which are so important for stability. In order to alleviate bone pain, doctors have for many years been using radio-isotopes. These are radioactive substances which accumulate in the area of the tumours. The radioactivity of the the standard substances used in the treatment does not, however, have enough energy to slow down the tumours, let alone to destroy them; their only effect is to alleviate pain.
Researchers of the Oak Ridge National Laboratory in Tennessee (USA) and the Clinic for Nuclear Medicine at the University of Bonn (Director: Professor Hans-Jürgen Biersack) have now developed a radio-isotope which emits far more high-energy radioactivity. For this purpose the researchers linked up radioactive rhenium-188 with a diphosphonate. The substance emits high-energy beta radiation which becomes weak enough after a few millimetres to become almost harmless. However, since proliferating bone metastases act like a magnet to radioactive phosphorus compounds, these collect near the cancer cells and can damage or even destroy them. At the same time the medication emits low-energy gamma radiation with a wide range. Nuclear medicine researcher Dr. Holger Palmedo explains: "By using a radio-sensitive camera we can thus check whether the diphosphonate is actually reaching those parts where it is supposed to."
Dr. Palmedo tested the substance in a wide-ranging study in which the Urology Clinic (Professor Peter Albers), the Medical University Clinic I (Professor Ingo Schmidt-Wolf) and the Institute of Medical Biometrics (Dr. Fimmers) were involved. The study involved a total of 64 patients suffering from cancer of the prostate and bone metastases. In all these cases the standard hormone therapy was no longer effective. One group of patients only received one injection of the new medication; those forming part of the second group were given it twice at an interval of eight weeks. The results were particularly promising in this second group: "In 39% the amount of the tumour marker PSA decreased by more than half - an effect which continued for at least 8 weeks."
PSA is a protein substance which the tumour cells produce. The more tumour tissue forms, the higher the PSA level is in the blood. A low PSA level therefore shows that the tumour is growing more slowly or is even retreating. After one injection the disease came to a standstill for an average of 2.3 months, after more than one injection this even increased to seven months. At the same time the survival rate of the patients to whom more than one injection was administered rose from seven to 13 months," is how Dr. Palmedo summarises the findings. Furthermore, the treatment does not have much in the way of side effects: "In some patients the blood count becomes a little worse, but the patients usually do not even notice this." A follow-up study is to investigate whether the positive results will be further improved if the new medication is administered three or four times.
Dr. Holger Palmedo
Clinic and Polyclinic for Nuclear Medicine of the University of Bonn
Tel.: ++49-228-2876973 or -5180