UCLA Journal of Radiation Oncology December First Edition - Flipbook - Page 8
UCLA RADIATION ONCOLOGY JOURNAL
prostate SBRT (and prostate radiation in
general) has thus required the placement
of metallic markers into the prostate.
Because of their metallic nature, these
markers can be seen on CT scans and the
prostate’s position can be triangulated
prior to treatment. MRI scans, on the other
hand, can clearly visualize the prostate
itself. A major technological advance
in the field of radiation oncology is the
development of linear accelerators that
have integrated on-board MRI scanners,
allowing direct MRI-guided radiotherapy.
For the treatment of prostate cancer, this
means not only that implanted markers
are not necessary, but also that the
prostate could be tracked “in-real time”
via direct visualization, allowing for a
much finer ability to adjust dose delivery
based on the prostate’s position. While CTguided SBRT is still an advanced, precise,
and cutting-edge technique, MRI-guided
SBRT has the potential to offer even more
precision. The MIRAGE trial is the first and
only trial of its kind to evaluate the benefit
of MRI-guided SBRT in a rigorous fashion.
Virtually any patient considering SBRT for
prostate cancer is eligible for this trial,
which is designed to show less urinary
side effects with MRI-guided therapy. This
trial opened in May 2020 and is rapidly
enrolling patients. The target enrollment
goal is 300 patients.
rising PSA levels after removal may
require postoperative radiation. As in
men who receive radiation alone, the
conventional course of radiation has
been the delivery of low daily doses over
the span of multiple weeks (in this case,
typically 35 to 40 treatments). Similarly,
the delivery of a higher dose per day may
allow treatment courses that are at the
least as effective and substantially more
convenient. Because of technological
considerations, the lack of a visible target
(since the disease being treated is usually
microscopic), and the fact that these
men have had to heal from surgery, the
study of SBRT in this setting has been
previously restricted to very small phase
I trials. Since March 2018, Dr. Kishan has
led the SCIMITAR study, which is the first,
largest, and at this time only phase II trial
investigating SBRT for these patients. This
trial is designed to deliver a biologically
higher dose to the areas at risk with the
hypothesis of improving recurrence-free
survival. On this study, men requiring
postoperative radiation receive five
treatments, delivered every other day.
These treatments can be delivered either
on a standard, CT-based linear accelerator
or on the aforementioned MRI-guided
linear accelerator. The latter has the ability
to better visualize the interface between
the target area, the rectum, and the
bladder, and potentially account for any
The second SBRT trial that Dr. Kishan
changes in anatomy that manifest from
is leading is called the SCIMITAR
day to day. Unlike the MIRAGE trial, this
(Stereotactic Intensity Modulated
RadioTherapy After Radical Prostatectomy) is not a randomized study, and all men
enrolled in the study will receive SBRT,
trial. This is a phase II trial that is
and may receive MRI-guided SBRT if that is
investigating the novel use of SBRT in
deemed appropriate. This SCIMITAR trial
patients who need radiation after radical
is designed to enroll 100 patients and has
prostatectomy (RP, surgical removal of
already enrolled 80.
the prostate). While RP is an effective
treatment, men who are found to have
The final trial that Dr. Kishan is leading
aggressive disease features or who have
is the GARUDA (Germline DNA-based
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