DISCUSSION
FOCAL CRYOTHERAPY
Cryosurgery is the term used to describe tissue destruction using extreme cold temperature.
The hystologic sequelae of this process are inflammatory reaction,
coagulative necrosis and finally fibrosis and scarring (9).
Focal cryoablation is an alternative therapy for the treatment of localized prostate cancer,
that provides precise targeted ablation of small tumors,
preserving the remainder of the uninvolved organ (3,4) (Fig.
16).
As it is not possible to document hystopatologically the complete tissue necrosis after cryoablation,
while PSA level comes out as bouncing and therefore not completely useful in the follow-up,
a radiological follow-up can be helpful (8).
Among the different imaging techniques,
MRI represents the ideal one since it is reproducible,
non operator dependent and optimally able to detect the difference between necrotic and still viable tissue.
Nevertheless,
usefulness of MR imaging follow-up of patients with prostate cancer treated with cryosurgery remains controversial (5,6,7,8).
In patients treated with focal cryoablation for localized prostate cancer,
cryolesions tipically appear to be hyperintense with a hypointense peripheral rim on T2w images,
due to the coagulative necrosis induced by cryotherapy.
The treated areas showed an increase in size 24 hours after treatment,
due to postcryosurgery prostate edema,
and a progressive decrease in size in the following controls,
due to fibrotic evolution of cryolesions.
After focal ablation,
prostate showed no significant vascularization of the treated zone,
while the periuretral and controlateral zone were spared,
on ce-MR images,
due to vasocostriction and thrombosis of distal arterioles and venules induced by cryotherapy.
In our study,
according to previous MR imaging studies performed on patients treated with cryotheraphy for small renal masses (10),
the most significant MR patterns in the follow up of prostatic carcinoma treated with cryosurgical focal ablation were the decrease in size with the passing of time and the complete ischemia of the treated area of the prostate,
while the periuretral and controlateral zone were spared.
The most effective MR techniques for lesions sizing and enhancement evaluation were TSE T2w and subtracted ce-TSE-FS T1w sequences.
FOCAL BRACHITHERAPY
Permanent low dose-rate brachytherapy has been recognised to be an alternative therapeutic option to radical prostatectomy as well as to conformal radiotherapy in patients with clinically localised carcinoma (7),
and recently focal brachytherapy was proposed in the treatment of select patients with low-to-moderate risk prostate cancer as a possible alternative to whole-gland treatment (6) (Fig.
18).
As it is not possible to document hystopatologically the efficacy of the treatment and PSA level results variable in the follow-up,
a radiological follow-up can be helpful (8).
Among the different imaging techniques,
MRI represents the ideal one since it is reproducible,
non operator dependent and able to detect the presence of still viable tissue.
MR imaging resulted an effective technique in the in the post implant dosimetric evaluation (Fig.
6).
MR imaging can also recognize the changes induced from the treatment.
In our study,
morphologic MR evaluation showed reduction in size of the treated area of the gland and diffuse reduction of signal intensity on T2w images due to parenchimal fibrosis and atrophy.
Dynamic ce MR evaluation showed reduction of the vascularization of the gland.
Radiation therapy seeds were seen as small foci of focal signal intensity void (Fig.
17).
CONCLUSIONS
Our medium term experience suggests that focal cryoablation and Focal Brachytherapy are safe,
well tolerated and minimally invasive therapies for localized prostatic carcinoma,
and MR can be an effective imaging technique in the follow-up of prostatic tumors treated with focal cryoablation and Focal Brachytherapy.
MR can be effective iafter focal cryoablation in the early evaluation of the effectiveness of the treatment (immediate feedback about size and geometry of the cryoinsult),
in the evaluation of possible complications and in the evaluation of patients with clinical or laboratory suspect of recurrence.
MR can be also an effective imaging technique in the follow-up of prostate tumors treated with Focal Brachytherapy,
in particular in the evaluation of post-implant dosimetry.
MR imaging can also play a role in the evaluation of patients with clinical or laboratory suspect of recurrence.