Complementary Therapies for Hormone Refractory Prostate Cancer
by Prof Ben L Pfeifer MD PhD and Prof Bernhard Aeikens MD
There is an ever-increasing demand for complementary therapies by patients with prostate cancer. Often, patients’ expectations of such treatments are too high. In particular, complementary treatment cannot replace the potentially curative methods such as radical
prostatectomy and radiation therapy.
During the early stages of the disease, when cancer growth is still confined to the prostate, complementary treatments are primarily intended to enhance recognized standard therapy practices. During the hormone refractory stage of the disease, however, complementary treatment has gained significance due to its low toxicity.
Prostate Cancer – Where do we Stand Today?
Prostate cancer is today the most frequent malignant tumour in men – more frequent than lung cancer. In the UK, 32,000 new cases are registered each year. In about 50% of these cases it can be expected that the disease progresses to an incurable stage and that in ten percent to 20% of the cases metastases can already be verified at the time of primary diagnosis. More than 10,000 men die each year from prostate cancer in the UK, the disease representing around 13% of the approximately 77,000 male deaths from cancer in this country. The prevalence of the disease is, however, much higher, since only a small number of prostate cancer cases is ever diagnosed due to slow growth and late appearance of the tumour. The increase in incidence can mainly be considered the result of improved screening procedure by means of prostate specific antigen (PSA).
Since mainly older men are affected by prostate cancer, and the age structure of most West European industrial societies continues to move towards longer life expectancy, the number of new cases of the most frequent type of cancer in men will also continue to increase. This trend is alarming; as we presently cannot offer any treatment for this disease which we know for sure will lead to cure, prolong life expectancy, or at least do the patient more good than evil. Demands will be made by increasingly better informed and critical patients on urologists, radiologists and oncologists to provide competent and objective information on the advantages and disadvantages of the therapeutic options available. This also includes complementary therapies, as more and more patients today are looking for less traumatic and less toxic treatment.
Present day potentially curative therapies, such as radical prostatectomy and radiation treatment, only make sense as long as the cancer is confined to the prostate and metastases have not developed. Unfortunately, these treatment methods lead in a high percentage of cases to unacceptable and permanent side-effects, e.g. erectile impotency in 60%-100%, rectal disorders in 15% – 40% and urinary incontinence in 10% – 30% of patients. Furthermore, with regard to ‘cure’, the results of treatment by these invasive methods are still unsatisfactory; recurrence rates of between 20% – 50% are reported.
The curative effect of local treatment methods, such as radical operation and radiation therapy, are largely dependent on correct patient selection. Current customary diagnostic procedures, however, often underestimate the extent of the disease, so that patients receiving surgery or radiation treatment are in reality no longer candidates for these methods of treatment, because their prostate cancer has spread from the organ and has already formed micrometastases. There is presently still no cure for metastatic prostate cancer, and the testosterone ablating therapies such as orchidectomy or the administration of LHRH agonists and anti-androgens frequently only achieve short-term tumour control (months to a few years).
Long-term results are unsatisfactory and most prostate cancer patients become hormone refractory. At this stage there is often fast progression of the disease and metastases develop. Various lines of initial treatment, such as newer combinations of chemotherapy, use of radioisotopes (e.g. samarium-153), blocking of growth factors by monoclonal antibodies, immune therapies (e.g. dendritic cell vaccines), angiogenesis blocking strategies, re-differentiation of cancer cells by means of retinoids and vitamin D analogues and finally gene therapy, are presently undergoing clinical trials for this particular situation, but up to now none of these measures has brought patients significant advantages.
