Biochemical Outcomes Following Prostate Brachytherapy with 5-year Minimum Follow-up: The Importance of Patient Selection and Implant Quality

Reviewer: William Levin, MD
OncoLink
Last Modified: October 7, 2002

Presenter: M.A. Kollmeier
Presenter's Affiliation: Mount Sinai School of Medicine, New York
Type of Session: Scientific

Background

  • One form of radiation therapy used in the treatment of prostate cancer is brachytherapy.
  • The use of this technique is relatively new, compared to standard external beam therapy.
  • Accordingly, clinicians are still trying to uncover which factors are most imortant in determining the outcome in patients undergoing this procedure.

Materials and Methods

  • This was a retrospective analysis of 243 patients with clinically localized prostate cancer who were treated with permanent radioactive seed implantation (I-125 or Pd-103).
  • Patients were stratified into risk groups (low, intermediate, or high) based on PSA, stage, and Gleason score (GS).
  • Median follow-up was 68 months (49-84)
  • Median pre-treatment PSA was 8.2 (1.3-189)
  • 78% of patients had a GS less than or equal to 6.
  • 49% of patients were stage T2a or less, and 51% were T2b-T2c.
  • 138 patients received I-125 and 105 patients received Pd-103 seeds.
  • At least 40% of patients got some form of hormal therapy.
  • Implant dose was defined as the D90 or dose delivered to 90% of the prostate volume on post-implant dosimetry.
  • Based on prior studies, patients were grouped into having either optimal or suboptimal D90.
  • Biochemical failure was defined using the ASTRO definition, 3 consecutive rises of PSA.

Results

  • 8-year actuarial freedom from biochemical failure (bFFF) was as follows: 80% for PSA < or equal to 10 ng/ml, 86% for PSA 10.1-20, 45% for PSA >20 (p=0.0001)
  • 8-year bFFF was 85% for GS < or = to 6, versus 61% for GS > or = to 7.
  • 8-y bFFF for the low risk group (T2a or less, GS 6 or less, inital PSA of 10 or less) was 88%, versus 65% for the high risk group (GS 8 or greater, or PSA 20 or higher, or at least 2 of the intermediate risk features.
  • Optimal dose implants (140 Gy or higher for I-125 and 100 Gy or higher for Pd-103) had an 8-y bFFF of 82%, versus 68% for suboptimal implants.
  • Hormonal therapy had no significant effect on outcome.
  • In multivariate analysis, statistically significant factors included: initial PSA, Gleason score, and dose group.
  • Low risk patients with optimal dose had a 5 year bFFF of 94%.

Author's Conclusions

  • The optimal candidates for prostate brachytherapy should be those patients with the low risk group features.
  • 5 year freedom from bichemical failure is excellent in this patient population.

Clinical/Scientific Implications

  • This study, which was done at an institution known for excellence in the field of prostate brachytherapy, helps define who is a reasonable candidate for this treatment.
  • Although the results for the low risk group are excellent, longer follow-up is needed to confirm efficacy.
  • This study also underscores the importance of proper technique and dosing.

Oncolink's ASTRO Coverage made possible by an unrestricted Educational Grant from Ortho Biotech.

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