Traditional methods of evaluating prostate cancer like rectal examination,
transrectal ultrasound,
sextant biopsies and prostate specific antigen (PSA) are able to predict indolent tumors and aggressive tumors.
However,
most patients are in an intermediate situation in which the accuracy of the above techniques is limited [1,
2].
Because of these limitations,
the accuracy of MRI in the study of local extension of prostatic cancer has been studied,
with encouraging results [3].
In the past decade,
the technology and prostate MRI has improved,
and also the experience of radiologists in viewing and reporting.
New techniques such as MR spectroscopy (MRSI),
the use of dynamic contrast,
the diffusion and perfusion techniques,
studies with high magnetic field,
the image processing,
and image and communication systems (PACS) have led to a breakthrough in the performance of the MRI in prostate cancer.
Both prostate MR images and spectroscopy can evaluate tumor aggressiveness.
It has been observed that the spectroscopic data and rates in spectroscopy studies correlate with Gleason Score.
Recent studies also have shown that some parameters obtained with MRI systems such as ADC (Apparent Diffusion Coefficient) and the T2 relaxation time,
correlated with tumor cellularity [4].
Today,
the fundamental use of this diagnostic tool focuses on macroscopic local staging of the disease.
This is important in order to know about the existence of prostate tumor nodules,
whether unilateral or bilateral and,
more important,
to establish whether there is extraprostatic extension or not,
since the presence of extension (stages cT3-T4) confers a poor prognosis of the disease [5,
6].
MRI can also detect in the same procedure nodal drainage areas and explore the pelvic bone structures to rule out nodal or bone metastases.
The probability of extraprostatic tumor extension (ETE),
infiltration of seminal vesicles,
and pelvic lymph node involvement can be determined clinically with the use of nomograms,
such as Kattan and Partin.
These nomograms estimate pathological stage based on pretreatment PSA level,
clinical stage and Gleason score in the specimen biopsia [1,
7].
Although the nomograms do not include the results of radiological examinations,
MRI can contribute greatly to improving the ability of the nomograms to predict the presence of ETE,
infiltration of seminal vesicles,
and lymph node metastasis.
Patients who would benefit most,
are those with intermediate or high risk.
Among the various irradiation techniques currently available for prostate cancer,
brachytherapy is the superior RT technique in terms of dose conformation,
that also allows greater dose escalation.
This technique has the quality of high-dose irradiation,
adjusting the isodose to the prostate with pinpoint accuracy,
keeping healthy adjacent organs,
such as the urethra and rectum,
in a tolerable dose range [8].
This extreme precision of brachytherapy requires a proper local staging of prostate disease for an excellent technique performance,
and techniques used today (as transrectal ultrasound) have not been able to provide more useful clinical information than the obtained by digital rectal examination [9].
We present the results of 50 patients with prostate cancer,
candidates for high dose rate brachytherapy (HDR),
who underwent prostate MRI,
and the implication of this technique in the local staging,
risk group classification and therapeutic decission.