20 Prostate Cancer

Prostate Cancer

7

THE GEC ESTRO HANDBOOK OF BRACHYTHERAPY | Part II: Clinical Practice Version 1 - 01/12/2014

HDR afterloading brachytherapy: Monotherapy Currently there is limited mature clinical data from using HDR monotherapy in the literature. The current data suggests HDR monotherapy may have advantages compared to other forms of therapy [16]; however, the results of ongoing studies are awaited. The current literature suggests it may be considered in all risk groups of prostate cancer including high risk disease. HDR monotherapy has also been advocated as a potential sal- vage treatment for local failures after seed implantation, surgery, primary hormonal-, or external beam treatments. In locally recurrent prostate cancer in case of technical eligibility salvage HDR or LDR implantations may be performed but again there is only very limited experience in the literature [16] and this should only be considered by experienced teams within defined protocols. The recommendations of the GEC ESTRO guidelines [17] are shown in table 21.3. Pulsed Dose Rate (PDR) afterloading brachytherapy There is currently limited experience in the use of PDR brachytherapy for prostate cancer. In principle the same indica- tions and contraindications as for HDR brachytherapy will apply. 6.2 Adjuvant hormone therapy Adjuvant hormone therapy has been shown to be of benefit when given with external beam radiation for locally advanced prostate cancer but this has not yet been demonstrated after brachythera- py. The main indication for hormone therapy in relation to LDR brachytherapy is prior to the procedure to reduce the volume of the gland before implantation [18]. When brachytherapy is used as a boost in combination with ex- ternal radiation, it is common practice to prescribe hormonal deprivation for intermediate and high risk patients where there is best evidence for a positive interaction [19]. LDR seed brachytherapy The volume to be treated includes the whole prostate within the confines of the capsule plus a 2 to 3 mm margin. Although the prostate is best visualised with MRI, the volume is usually de- fined by transrectal ultrasound with the patient in the treatment lithotomy position to determine the prostate volume. HDR afterloading brachytherapy Unlike seed brachytherapy for HDR brachytherapy the CTV will be defined after insertion of the needles or catheters. The defi- nition of the HDR CTV is the same as for LDR seeds to include the prostate capsule with a 2mm margin. This will be further extended if there is extracapsular or seminal vesicle disease to include those areas also. A subvolume (CTV2) which includes the peripheral zone of the prostate and maybe other areas in the prostate or periprostatic areas which are involved by the tumour may also be defined as a CTV 3 [17]. Functional imaging in- cluding Doppler sonography, dynamic contrast enhanced CT or MR, MR Spectroscopy or choline PET may be incorporated to enable planning of biological subvolumes which will be desig- 7. TARGET VOLUME

Table 21.3: Indications for HDR brachytherapy combined with external beam radio- therapy

Inclusion criteria Stages T1b–T3b Any Gleason score Any PSA level

Exclusion criteria TURP within 3-6 months Maximum urinary flow rate (Qmax)< 10 ml/sec IPSS > 20 Pubic arch interference Lithotomy position or anaesthesia not possible Rectal fistula

of TURP. Patients with benign prostatic hypertrophy and a large gland volume of greater than 50-60 cm 3 but otherwise suitable, can be downsized with three to six months of neo-adjuvant hor- mone therapy. The volume reduction in general will be between 30 and 50%, hence very large volumes will be excluded unless there is clearly no evidence of pubic arch interference for im- plant. Patients with IPSS <10 will do well after seed implantation, those with IPSS 10-20, have a higher chance of acute retention and patients with IPSS >20 should be offered another treatment modality. Urodynamic studies can further help to select patients who are at high risk for retention. Patients with a history of TURP still can have LDR brachytherapy, but a period of 6 to 12 months to allow for healing should be given. MRI or ultrasound should be used to assess the tissue deficit and where there is a large cav- ity brachytherapy may be contraindicated. This is currently un- der evaluation and new planning protocols to accommodate the TURP cavity have been described [13]. Recent TURP before or after seed implantation is associated with a higher than usual risk for incontinence. HDR afterloading brachytherapy The most common application of HDR afterloading is as a boost in conjunction with external beam therapy, however there is in- creasing interest in its use as monotherapy also. HDR afterloading brachytherapy: Boost High dose radiotherapy alone achieves good rates of biochem- ical control and cure in locally advanced prostate cancer with acceptable levels of acute- and late radiation toxicities [13]. Comparing treatment results of ultra-high-dose IMRT alone to IMRT combined with HDR brachytherapy, the combined treat- ment schedule resulted in improved PSA disease free survival. The greatest advantage of EBRT combined with brachytherapy boost seems to be seen in intermediate-, and high-risk groups of patients [14][15]. Combined external beam radiation and temporary brachyther- apy boost is also effective in low-risk cases but LDR brachyther- apy as monotherapy is as good. Comparing LDR (permanent seed) brachytherapy to HDR (temporary) brachytherapy as a boost complementary to external beam radiation there may also be additional advantages in economics and quality assurance in favour of temporary brachytherapy.