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Candidates for seed implantation depend on a number of considerations:

also see the American Brachytherapy Society (ABS) Recommendations for Prostate Seed Implants

Implants are ideal for tumors that are confined to the gland (within the capsule of the gland.) The risk of cancer being outside the gland is higher based on the stage, the PSA or the Gleason score (see the Partin tables and data from the Mayo Clinic)

Other considerations:


1. local anatomy
- the gland should not be too large (> 50 - 60 ml, the normal prostate gland is about 30ml, go here), should not have a large TURP defect, or the malignant nodule located in an area difficult to implant. the success of the implant depends on an even distribution of the seeds (otherwise it is safer to combine the implant with external beam radiation which will even out the "hot spots and cold spots")
2. risk of regional spread - from Partin Data, PSA > 10. GS > 6 or stage > T2a, or high risk path findings (e.g. vascular invasion or diffuse disease) all increase risk of some regional spread and the need for combing the seeds with external beam irradiation (EBT)
3. risk of distant spread - patient at high risk for distant metastases (GS 8 or higher or PSA > 15-20) would be candidates for systemic therapy (i.e. hormonal therapy e.g. Lupron +/- Casodex or Flutamide)
(note that the results with implants alone are poor in higher risk groups, see results page.)
 
Category Implant External Beam Hormones
Low Risk 145Gy I-125 or 125Gy Pd 103 None None
Medium Risk 110Gy I-125 or 100Gy Pd 103 45Gy Yes or No
High Risk 110Gy I-125 or 100Gy Pd 103 45Gy Yes
  Go here for a more detailed discussion of the proper dose and selection

Low Risk = favorable anatomy, PSA < 10, GS 6 or less, stage T1c or T2a, no adverse pathologic findings (no perineural  invasion and tumor confined to one lobe.) some would restrict low risk to Gleason score of 6 or less as in RTOG below

Medium Risk = PSA > 10 or GS 7 or higher, stage > T2a, unfavorable local anatomy, high risk path report

High Risk = Gleason Score of  8 or higher, PSA > 20

Note: there is still controversy over the merits of Palladium versus Iodine. Also combining therapy can increase the risk of complications, particularly impotence as noted: risk of impotence with seeds alone (~ 20%) with seeds + external beam (~ 25 - 30%) and with seeds + hormones (=/- external beam, risk is ~ 55%.)

There also is controversy over whether it is really necessary to add external beam to seeds in the intermediate risk group. The current RTOG trial (0232) is randomizing intermediate risk patients (Gleason 6 with PSA 10 - 20 or Gleason 7 with PSA <10, and volume < 60 cc) to either implant alone (125Gy Pd-103 or 145Gy I-125) or combination (45Gy EBT Plus either Pd-103 (100Gy) or I-125 (110 Gy.)

 
As noted patients treated with implant alone, must have ideal anatomy (small gland, not TUTP defect) and early cancer that is likely confined to the gland (not outside the capsule) The eligibility criteria from the current RTOG trial (RTOG 98-05) is noted:

PHASE II TRIAL OF TRANSRECTAL ULTRASOUND GUIDED PERMANENT RADIOACTIVE IMPLANTATION OF THE PROSTATE FOR DEFINITIVE MANAGEMENT OF LOCALIZED ADENOCARCINOMA OF THE PROSTATE Patients will receive I-125 permanent implantation of the prostate, 146 Gy (TG 43)

Eligibility Criteria:
- Histologically confirmed, locally confined adenocarcinoma of the prostate
- Clinical stages T1b - T2a
- No clinically or pathologically involved lymph nodes
- No distant metastases
- Karnofsky Performance Status > 70
- No prior chemotherapy, pelvic radiation or any hormonal therapy, including Proscar
- PSA is mandatory, must be < 10 ng/mL
- No prior TURP
- Prostate volume by TRUS < 45 cc
- No significant obtructive symptoms; AUA score must be < 18
- No hip prosthesis
- Combined gleason score < 6

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