Newer radiation treatments--brachytherapy and conformal radiotherapy--were
discussed at a symposium at the 1996 meeting of the American Society for
Therapeutic Radiology and Oncology (ASTRO) in Los Angeles.
Kent Wallner, MD, of Memorial Sloan-Kettering who has been implanting
radioactive seeds for eight years, reported that tumor control rates with
implantation are quite similar to the rates achieved with radical prostatectomy--at
least over a 6-year period following the therapy. "Of course, these
results need to be verified, but I think that radioactive seed implantation
will very soon begin playing a more prominent role in the treatment of
prostate cancer," he said.
The treatment has a number of advantages. It can be performed on an
outpatient basis; it allows most men to go back to work within a few days;
and it appears to preserve potency. All of the men under age 60 who were
able to achieve erection before seed implantation remained potent 5 years
after treatment, while 80% of those over 60 retained their ability to have
Three-Dimensional Conformal Radiotherapy
Gerald E. Hanks, MD, chairman of radiation oncology at Fox Chase Cancer
Center in Philadelphia, described the results of a study in which 233 men
were treated with three-dimensional conformal radiotherapy (3D-CRT). The
success rate at five years, as measured by a stable PSA level, was comparable
to that of men treated with surgery at Johns Hopkins and M. D. Anderson.
The 3D-CRT caused fewer side effects and preserved sexual function better
than traditional radiation therapy, Dr. Hanks said.
Dr. Zvi Fuks, chairman of radiation oncology at Memorial Sloan-Kettering,
who conducted the 3D-CRT study along with Dr. Hanks, discussed the possibility
of increasing the dose of radiation by 10%. "The increase may be possible
because 3D-CRT gives greater protection to healthy tissue," noted
Dr Malcolm Bagshaw, professor emeritus at Stanford University School
of Medicine, who pioneered the use of external-beam and linear accelerator
treatment, observed that "the standard dose of 70 Gy is really quite
a high dose in its own right. It is possible to increase the dose, but
to what extent we don't really know yet. It would be important to increase
the dose as high as can be achieved without increasing unwanted side effects.
I think that for the time being, when a dose of 70 Gy is exceeded, it should
be achieved in a clinical trial by people who are treating with a well-developed
protocol and escalating the dose very cautiously.
Improvements in Traditional Radiotherapy
"We're seeing an absolute technical explosion in the development
of linear accelerators, computer control of linear accelerators, better
ways to plan the treatment and better ways to calculate the dosage,"
noted Dr. Bagshaw. Treating prostate cancer patients who are considered
good candidates for radical surgery with external-beam radiation instead,
is yielding the same long-term survival (15 years and longer) as surgery,
Traditional radiotherapy may also have new applications. A pair of studies
determined that traditional therapy could be effective for early-stage
disease. The Cleveland Clinic study of 400 men with early-stage prostate
cancer indicated that regardless of whether surgery or radiation was chosen,
the same percentage in each group were recurrence free after 5 years. At
the University of Michigan, Ann Arbor, 93 men who were candidates for prostate
surgery were treated with traditional therapy instead. Five years after
treatment, almost 99% showed signs of recurrence, a rate identical to that