Prostate Cancer
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Benefits and drawbacks of specific approaches
Intensity modulated Radiotherapy (IMRT)
IMRT has emerged as the preferred external beam radiotherapy (EBRT) method, superior to standard three-dimentional conformal radiotherapy (3DCRT), due to its spatially superior dose conforming capability, translating to an improved ability to deliver a very high dose of radiotherapy to the prostate, while better sparing the encroaching rectum from the high dose region, significantly reducing the incidence of delayed rectal toxicity, particularly when a dose of greater than 75Gy is delivered (10, 11).
Compared with lower dose EBRT methods, high dose IMRT has produced improved disease-free survival (10, 11). Another randomized radiation dose escalation trial demonstrated the superiority of high dose EBRT (79.2Gy) compared with “conventional dose” EBRT (70.2Gy), using proton beam therapy as the prostate dose escalation method (12). Proton beam therapy conforms the high dose volume comparably to IMRT. These two trials have established high-dose radiation therapy, preferably delivered by IMRT or proton beam, as the preferred EBRT method.
Against the benefit of IMRT, as with all treatments, there are drawbacks, primarily including a two month time frame to deliver a full therapeutic course, plus a symptomatic recovery period that follows over the next several months. Although rectal injury is less frequent with IMRT, relative to the radiotherapeutic approaches of its predecessors, it is still possible. There is also a substantially higher cost of IMRT compared with standard 3DCRT.
Intensity Modulated Radiotherapy (IMRT):
Demonstrating sparing of the rectum
from the high dose region
Written by Donald B. Fuller, M.D. – Radiation Oncologist