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The Prostate Cancer InfoLink

External Beam Radiotherapy in the Management of
Hormone-Refractory Prostate Cancer

Last Revised January 20, 1996
[Developments in radiotherapy since this was written may change the information.]

Introduction | General overview | Local field radiotherapy | Wide-field radiotherapy | Combining external beam and injectable radiation therapies | Future possibilities

Introduction

Editorial note: This introduction is very similar to that at the beginning of the section on use of injectable radiopharmaceuticals in the management of hormone-refractory prostate cancer patients and can be skipped if you have already read that section. [Note was on original page.]

The value of radiation therapy in the management of metastatic prostate cancer lesions is undisputed. Basically, three forms of radiation therapy are available for management of such lesions: local field external beam radiation, wide-field external beam radiation, and the use of injectable radiopharmaceuticals. The use of injectable radiopharmaceuticals such as strontium-89 (Metastron) has been addressed in a separate section.

In the past, about half of all newly diagnosed prostate cancer patients presented with evidence of metastatic prostate cancer, and in the majority of those patients, the metastases included bone metastases. However, with the introduction of the PSA test it appears that only about 30% of patients diagnosed now have any clinical symptoms suggestive of prostate cancer, and (at least in the US) metastatic bone disease in newly diagnosed patients is becoming relatively rare. However, 85% of the men who die of prostate cancer in the US (which is 3% of the men diagnosed with the disease) have bone metastases. On the basis of the 1995 estimate of 240,000 newly diagnosed patients, this implies that at least 6,000 of that 240,000 will go on to die of the disease with bone metastases.

In other sections we have seen how hormonal therapies of differing types are commonly used to delay the progression of advanced prostate cancer and extend survival while improving the quality of life for many patients. (For links to such sections, please return to the overview on the treatment of advanced disease). However, there are some patients for whom such therapy is insufficient. In many such patients the use of radiotherapy can give relief from bone pain, at least temporarily, when properly implemented.

This section will not attempt to address the details of implementation of external beam radiotherapy for the management of metastatic bone disease in patients refractory to hormonal therapy. Rather, it will summarize the most critical issues that patients and family members may need to appreciate when this type of therapy is offered or recommended.

General overview

Two types of external beam radiotherapy have been used in the management of patients with symptoms caused by one or more metastatic lesions or with spinal cord compression resulting from spinal metastases: local field radiation, in which a narrow beam of radiation is directed at the specific metastatic site or sites, and wide-field radiation. Customarily, local field radiation has tended to be used for patients with a long life expectancy and fewer metastatic sites and wide-field radiation has been used more with patients with a shorter life expectancy and multiple metastatic pain-causing sites.

A wide range of factors must be assessed by the physician in making recommendations regarding the specific form and dose of radiation to be given to individual patients. The more obvious such factors include

  • The patient's functional status and probable life expectancy
  • The whereabouts of the metastases (e.g., spine, legs, arms, shoulders, ribcage, other organs, etc.)
  • The size and number of the metastases and the degree of pain caused to the patient by these metastases
  • The possible complications which could affect treatment.

Patients and family members should be aware that patients with severe or potentially severe complications caused by their bone metastases are unlikely to be acceptable candidates for treatment with any form of radiation therapy alone. These patients are likely to need surgical interventions (e.g., orthopedic surgery or neurosurgery) in addition to local field radiation. The types of complication which would be likely to require this type of intervention include bone fractures and certain types of spinal cord or nerve compression resulting from the metastases.

Major studies have shown that local field radiation therapy can offer some degree of pain relief to 80-90% of patients (although patients will frequently need retreatment at a later date, either for recurrence of pain in the same lesion or for pain caused by newly apparent lesions). Similarly, wide-field radiation offers subjective pain relief to about 60-80% of patients. Patients need to appreciate, however, that such pain relief is inevitably temporary (usually of the order of 20-50 weeks); how long it will last is highly dependent upon the individual patient and the precise nature of his metastases.

Local field radiotherapy

Local radiation is implemented following appropriate imaging studies (X-rays, CT scans, MRIs, or bone scans, as appropriate) which are required in order to identify the precise location and extent of the metastatic site or sites. Current radiotherapeutic techniques allow highly accurate focusing of differing types of radiation based upon the exact location and nature of individual pain sites.

It must be noted that there is considerable variation in the degree of pain relief which any particular patient may experience as a consequence of receiving local field radiation. This wide variation is a direct result of the very different ways in which a metastatic site may develop in the bone or other organs of individual patients. Some patients may gain high degrees of pain relief from this type of therapy for significant periods of time; others may not be so lucky.

There now appears to be general agreement in the radio-oncology community that there is no particular benefit to high-dose, fractionated radiotherapy as compared to single-dose therapy or short-course, low-dose radiotherapy in the management of pain-causing metastases. It does appear to be clear, however, that the patients who are able to gain complete relief from pain symptoms through the use of this type of therapy will have significantly longer-lasting relief those patients who only gain partial relief. Some literature appears to suggest that patients who are generally in good health and have limited metastatic disease will do better if they receive higher doses of radiation delivered in multiple fractions.

Wide-field radiotherapy

As stated earlier in this section, wide-field radiation is most appropriate for patients who have multiple metastatic pain-causing sites of prostate cancer. Wide-field radiotherapy can take one of several different forms:

  • Radiation to the entire upper half of the body
  • Radiation to the entire lower half of the body
  • Radiation to the mid-section (from the upper thighs to the lower chest)
  • Sequential hemi-body radiation, in which half of the body is radiated in one session and the other half in a later session, thus allowing the bone marrow from the unirradiated half of the body to grow and replace the lethally irradiated marrow in the other half prior to the second session.

Patients normally have to meet a number of criteria to be eligible for this type of radiation therapy, including
  • A life expectancy of 6 weeks or more
  • Age of 75 or less (although exceptions are common if the patient is considered to be sufficiently medically fit)
  • Reasonable health status
  • No prior heart damage (for upper body radiation).

Patients who have previously received local field radiation can go on to receive wide-field radiation if this is considered appropriate.

The potential benefit of wide-field radiation for the patient is that it becomes possible to treat multiple symptomatic sites with a lower number of patient visits. In addition, there are some data to suggest that wide-field radiation may be associated with a lower frequency of retreatment. As indicated previously, wide-field radiotherapy is associated with some degree of pain relief in 60-80% of patients, and more than half of the patients will gain the benefit of such pain relief within approximately 48 hours of treatment. Approximately 20-25% of patient can expect to gain complete pain relief.

Wide-field radiotherapy can be repeated in appropriate patients, and outcomes appear to be similar following repeat treatments to the outcomes observed after the initial treatment. In other words, for those patients who respond well to wide-field radiation at a first treatment, a second treatment is likely to have a good response too, should it prove necessary.

Combining external beam and injectable radiation therapies

One recent trend has been the combination of local field radiotherapy with the use of injectable radiopharmaceuticals such as strontium-89. For information on this form of combination radiotherapy, please see the section on the use of injectable radiopharmaceuticals.

Future possibilities

Technical improvements in the ability to manipulate and deliver different types of radiation with greater and greater accuracy may impact the value of radiotherapy in the management of hormone-resistant prostate cancer over time. Another possibility is that the development of "radiosensitizers" (pharmaceuticals which make cancerous tissues more sensitive to radiation than normal tissues) or "radioprotectants" (pharmaceuticals which can protect normal tissues from the side effects of radiotherapy) may impact the quantity of radiation which can be delivered to patients while lowering the degree of risk from hematologic side effects which currently are the normal limiting factors in the use of radiation therapy.

Another possibility that is being actively evaluated is the earlier use of different types of radiotherapy in combination with continuing hormonal therapy in attempts to further prolong survival in patients with asymptomatic but localized bone lesions.


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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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