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The Prostate Cancer InfoLink


The Use of Suramin in the Treatment of
Hormone-Refractory Prostate Cancer

Last Revised January 6, 1996
[Note: developments since this was written may change the information.]

Introduction | The questions that have been answered | The predicted clinical uses | Adverse reactions to suramin | Concluding remarks

Introduction

The use of suramin as a drug for the treatment of parasitic infestations dates back to the early years of the 20th Century. Although it was an effective form of treatment, it was also associated with a significant number of well recognized but potentially severe side effects and the added drawback that it has to be given intravenously. (It is not available in an oral formulation.)

Recent interest in the activity of suramin as a form of therapy for patients with advanced prostate cancer resulted from investigation of suramin as a promising compound for the treatment of patients with acquired immunodeficiency syndrome (AIDS). Although suramin was found to have no clinical value in the management of patients with AIDS, it was noted suramin appeared to induce adrenal insufficiency and that it appeared to have effects on growth factors involved in prostate cancer cell growth.

Extensive studies have now been carried out to improve our understanding of the mechanisms of action of suramin and how we can avoid the serious side effects which have been commonly observed in the past. The Prostate Cancer InfoLink does not intend to provide a detailed analysis of this information. Rather, for patients and interested health professionals, it is perhaps more important to understand the potential uses for this product based on the expected results of clinical trials which are nearing completion and publication.

The questions that have been answered

One of the first questions that had to be answered regarding the use of suramin in the treatment of advanced prostate cancer was whether researchers could find an appropriate and useful dose of the drug which produced effective clinical responses in patients with a minimum level of adverse reactions.

Two basic approaches have been taken to this question. The first approach has assumed that drug levels of suramin must be titrated (managed) on a patient by patient basis or that a dosing schedule could be developed which would maintain plasma levels of suramin between acceptable levels to provide therapeutic efficacy without risk of serious adverse reactions. The second approach was to seek a standard therapeutic dose of suramin which would be clinically effective and safe in the vast majority of patients. These studies are still going on. However, it appears that both approaches may be successful. One large clinical trial has now been completed which was designed to evaluate the relative value of suramin at three different doses (600, 1000, and 1400 mg/m2 per day. Other studies have shown that it is possible to maintain certain plasma concentrations of suramin. Clearly, it would be easier if it was possible to determine a specific dose of suramin that was effective and safe for the majority of patients.

A second question that has had to be addressed is the necessity for adjuvant therapy with glucocorticoids and mineralocorticoids (different classes of corticosteroids). Because suramin clearly induces adrenal insufficiency in the majority of patients, it now appears probable that patients receiving suramin will certainly need adjuvant therapy with low-dose hydrocortisone and possibly with other agents.

The predicted clinical uses of suramin

Clinical researchers are currently awaiting the results of two major randomized prospective trials designed to evaluate the potential future uses of suramin.

The first of these two trials has been designed to test the use of suramin + hydrocortisone in the treatment of patients failing combined hormonal therapy. This has always been the setting in which most clinicians felt that suramin was most likely to have clinical value if an appropriate dose could be established.

The second trial has been designed to test the use of suramin + hydrocortisone in the treatment of patients with stage M+ (stage D2) prostate cancer who have never received hormonal therapy of any type. This trial will only provide us with useful information if it compares this form of therapy to complete hormonal therapy in a comparable patient group.

Adverse reactions to suramin

Under no circumstances should patients or health professionals overlook the fact that historically suramin has been associated with a series of potentially serious side effects. These side effects appear to be closely correlated with the plasma levels of suramin in individual patients.

Although recent studies have allowed clinicians to significantly reduce the incidence of severe side effects, suramin has been associated with dose-limiting malaise and fatigue, coagulopathies, sensory and motor neurotoxicities, parasthesias, neutropenia, anemia, lymphopenia, thrombocytopenia, and a whole range of other adverse reactions. The incidence of these adverse reactions in randomized clinical trials will be important to our understanding of the potential uses of this drug.

Concluding remarks

The Prostate Cancer InfoLink expects to see publication of the results of randomized clinical trials of suramin in different patient populations in 1996 and 1997. Whether these trials will definitively indicate a place for suramin in the treatment of some patients with advanced prostate cancer is still open to question. Information received by The Prostate Cancer InfoLink has suggested that suramin may offer a significant survival benefit in some patient groups. However, as yet there is no published data to support this preliminary information.

It seems very probable to The Prostate Cancer InfoLink that suramin will indeed prove to be a drug which can induce significant clinical responses in some patients with prostate cancer. The question is going to be whether the risk of adverse reactions associated with suramin can be managed down to a sufficiently low level that the possibility of effective treatment is associated with a high probability of successful outcome outside very carefully controlled clinical trials.


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The content in this section of the Phoenix 5 site was originally developed by CoMed Communications (a Vox Medica company) as part of The Prostate Cancer InfoLink. It is reproduced here with the permission of Vox Medica.

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