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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