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What is Intermittent Hormonal Therapy?

Last Revised December 5, 1995
[developments in hormone therapy since 1995 may change this material]

Introduction | Benefits and risks | Current recommendations for intermittent CHT


The concept of intermittent hormonal therapy is not new. Whitmore and some of his colleagues attempted to apply the principle of this type of therapy using diethylstilbestrol (DES) in the 1970s. However, the drugs then available were not appropriate to this type of hormonal manipulation and the patients also may not have been early enough in their disease.

The basic concept behind intermittent hormonal therapy for advanced prostate cancer is very simple. Combined hormone therapy is first used to lower the patient's PSA level. If the PSA level stabilizes at an appropriately low level, treatment is stopped and the patient's PSA is carefully monitored. Should the PSA start to rise again, the combined hormone therapy is reinitiated. In theory this cycle of events can be repeated multiple times.

Intermittent hormonal therapy has been given a new lease on life by the availability of the LHRH agonists and the nonsteroidal antiandrogens. In the early 1990s, Goldenberg and his colleagues in Vancouver, Canada, carried out the work which gave the momentum for current and extensive trials to ascertain the real clinical value of this technique.

Benefits and risks

Intermittent hormonal therapy comes with a number of potential benefits and a number of potential risks. It is important for the patient to understand these.

Potential benefits

The potential benefits of intermittent hormonal therapy are largely to do with the patient's quality of life. The following is a general list of the more important perceived benefits:

  • When the patient is off therapy, he will normally recover sexual function, thus overcoming one of the major perceived drawbacks of hormonal therapy for advanced prostate cancer, which is impotence.

  • When the patient is off therapy, he will not suffer from the other common side effects of treatment with LHRH agonists and antiandrogens (e.g., hot flashes, gynecomastia, loss of muscle tone, gastroenterological problems, etc.), and will thus have an improved quality of life.

  • Reduction in the overall quantity of hormonal therapy may reduce the likelihood of the proliferation of androgen-independent prostate cancer cells and thus the likelihood of development of hormone resistance.

Potential risks

By contrast, the only real risk associated with the use of intermittent hormonal therapy is that the disease may progress faster because of its ability to progress while the patient is not actively receiving treatment.

Assessing the risk/benefit equation

As is often the case in assessing how to treat prostate cancer, doctor and patient are faced with a decision about their valuation of the potential benefits as compared to the potential risks. The patient who values life at all costs, regardless of the quality of that life, is likely to consider (based on currently available data) that continuous long-term hormonal therapy is most likely to offer him the longest possible survival opportunity. On the other hand, the patient who values life only if it comes with certain levels of quality may be more likely to consider that intermittent hormonal therapy is a reasonable option to think about.

Current recommendations for intermittent CHT

[Reminder: This was written in 1995.]

There are, as yet, no absolute recommendations for "correct" methods for carrying out intermittent hormonal therapy. This form of therapy is still experimental, and a number of clinical trials are either in progress or in the development stage. The Prostate Cancer InfoLink wishes to emphasize that the true value of intermittent hormonal therapy will only be known when we have data that clearly indicate the survival opportunity available using this type of therapy and the associated adverse reactions to the pharmaceuticals used.

Having said that, the following generalized protocol indicates the type of treatment program which is being tested or is under discussion as a method of testing the value of intermittent hormonal therapy. It could be several years before the true value of such a protocol is known.

  • Patients with advanced prostate cancer (stage D2 or M1) are eligible. They must have received no prior long-term hormonal therapy (and in some trials no prior hormonal therapy at all).

  • The patients are randomized to receive either standard CHT or intermittent CHT. CHT is normally given in the form of monthly LHRH agonist injections together with oral nonsteroidal antiandrogen therapy.

  • All patients are initially treated for a period of 1-3 months unless they either show clear signs of disease progression and must be withdrawn from the trial or they have to withdraw from the trial for some other reason (e.g., adverse reactions to pharmaceuticals).

  • Patients receiving intermittent CHT, and whose PSA level drops to below 4 ng/ml (i.e., to normal levels), are maintained on CHT for a total of 6-8 months until the physician is sure that the PSA has stabilized at this normal level.At this point their therapy is stopped. (The patients in the so-called "control group" who are receiving continuous hormonal therapy for purposes of comparison are maintained on their CHT throughout the trial.)

  • Once therapy has been stopped, intermittent CHT patients are monitored on a regular basis for any indication that their disease has started to progress again. (The commonest sign of such progression is a rising PSA.)

  • The PSA of patients receiving intermittent hormonal therapy is normally allowed to rise to a previously determined level (e.g., 20 ng/mL). Once it reaches that level, the entire cycle of combined hormonal therapy, stabilization of PSA level, cessation of therapy, etc., can be reinitiated.

The objective here is to determine whether stopping and starting CHT is as good or better than continuous CHT with respect to the development of hormone-resistant prostate cancer, the ultimate survival of the patient, and the quality of life of the patient throughout this period of time.

There are many centers at which intermittent hormonal therapy is being tested in a variety of forms. Patients who are interested in the possibility of participating in clinical trials of this type of therapy should consult their doctors. Patients who wish to receive this type of therapy without participating in clinical trials can also ask their doctors about this. The Prostate Cancer InfoLink has been informed that some physicians will already provide this type of therapy to appropriately informed patients, usually with the understanding that there are few data to support the long-term survival benefits of this type of therapy at this time.

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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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