| Tracks 1-13 |
| Track 1 |
Introduction |
| Track 2 |
Key issues in multimodality
radiation therapy and hormonal
therapy for high-risk disease |
| Track 3 |
Impact of tumor grade and
proliferation on response to
radiation therapy |
| Track 4 |
Dose, administration and
tolerability of radiation
therapy and hormonal therapy |
| Track 5 |
Community variation in the
quality of radiation therapy
for prostate cancer |
| Track 6 |
Advances in the use of image-guided
radiation therapy |
| Track 7 |
Selection and duration of
hormonal therapy combined with
radiation therapy |
|
| Track 8 |
High-dose bicalutamide as
a potential alternative to total
androgen blockade |
| Track 9 |
Optimal dose of radiation therapy
and duration of hormonal therapy
for high-risk disease |
| Track 10 |
Selection of patients for brachytherapy
versus external beam
radiation therapy |
| Track 11 |
Androgen deprivation for patients
with intermediate-risk disease |
| Track 12 |
Treatment of patients with
PSA-only progression |
| Track 13 |
Radiation therapy for patients
with positive margins after
prostatectomy |
|
|
Select Excerpts from the Interview
Track 3
DR LOVE: What do we know about the relationship between disease
characteristics, such as tumor grade and degree of differentiation, and
response to radiation therapy?
DR ZELEFSKY: It is thought that people with high-grade disease are less likely
to respond to low or conventional radiation doses, and the data suggest that
higher irradiation doses are needed to eradicate greater volume or bulk disease.
In other words, a dose response exists for volume of disease, and higher radiation
doses are necessary.
Poorly differentiated tumors or more aggressive tumor clones appear to require
higher radiation doses. They may also require radiosensitizers to overcome an
inherent radioresistance.
Evaluating tumors in general, we know that more rapidly doubling tumors
with greater proliferation are less responsive to radiation therapy. For these
types of tumors we sometimes hyperfractionate, give twice-daily treatment or
combine the radiation with systemic therapies. However, this is not well established
in prostate cancer.
Track 4
DR LOVE: In a clinical setting, how do you approach individualizing the
dose and schedule of radiation therapy in patients with high-risk or locally
advanced disease?
DR ZELEFSKY: We use hormonal therapy in conjunction with radiation
therapy. If we are administering external beam radiation therapy in conjunction
with hormones, we use a high radiation dose. At our institution, we
generally use intensity-modulated radiation therapy (IMRT) as our best tool
for delivering that higher dose safely. We use dose levels of about 81 to 86
Gray, and we administer hormonal therapy prior to, during and after radiation.
DR LOVE: What do we know about the toxicities as the dose of radiation
therapy is increased?
DR ZELEFSKY: It’s expected that as you increase the dose, you may get higher
rectal and urethral-related toxicities. Fortunately, at least for rectal toxicities,
IMRT reduces rates of rectal bleeding and serious rectal complications.
Even with the delivery of high doses, the risk of serious injury is only about
one percent or less, and the incidence of rectal bleeding is about three or four
percent.
Track 7
DR LOVE: When androgen deprivation is used with radiation therapy, a
lot of variation occurs in the duration of administration and the type of
endocrine therapy utilized. What options do you think are reasonable to
discuss with patients, and how do you decide how to treat an individual
patient?
DR ZELEFSKY: The many schedules used for androgen deprivation in
conjunction with radiation therapy have been reported in published randomized
trials, such as the RTOG-8610 trial, which established for the first time a
role for androgen deprivation in combination with radiation therapy, showing
an improvement over radiation therapy alone when administered two months
before and during radiation treatment (Pilepich 2001).
Subsequent RTOG trials and the EORTC trials confirmed this benefit,
showing an advantage to using adjuvant hormonal therapy for two years, three years, indefinitely or, most recently, six months as shown in Anthony
D’Amico’s trial for patients at intermediate risk and selected patients at high
risk (Bolla 2005; Zelefsky 2006a, 2006b; D’Amico 2004; [2.1]).
No established protocol or appropriate schedule has emerged for androgen
deprivation. In general, most radiation oncologists and urologists use hormonal
therapy before or during at least the course of radiation treatment and probably
for about six months afterward for patients at high risk.
Select publications
