The long-term results of RTOG 98-05 — an innovative brachytherapy trial


The recently published long-term results of RTOG 98-05 illustrate at least one way in which we can start to get better insight into the effectiveness and safety of new forms of treatment for localized prostate cancer as compared to older forms of treatment — without having to conduct complex and socially difficult randomized clinical trials.

The goal of RTOG 98-05 was to investigate the long-term effectiveness of transrectal ultrasound-guided implantation of permanent radioactive seeds of iodine-125 as a treatment for low-risk, organ-confined prostate cancer and to compare the outcomes to historical outcomes data for prostatectomy and external beam radiotherapy. However, what was unusual was the attempt to do this within a highly controlled cooperative group trial setting.

This was only a relatively small, Phase II clinical trial and is best understood to be a pilot study to explore the practicality of this type of clinical trial.

Lawton et al. have now reported that all patients accrued to this study had adenocarcinoma of the prostate of clinical stage T1b, T1c, or T2a, with no evidence of nodal or metastatic disease; PSA levels were all ≤ 10 ng/ml, and patients all had Gleason scores of ≤ 6. By design, the study enrolled patients from several different institutions, and no one institution could accrue more than 8 patients to the study.

The outcomes of the study to date are as follows:

  • A total of 101 patients were enrolled in the trial at 27 different institutions.
  • 94/101 patients were actually eligible for data analysis.
  • The average (median) follow up was 8.1 years (range, 0.1 to 9.2 years).
  • 8 patients had protocol-defined biochemical progression.
  • 5 patients had local failure.
  • 1 patient had distant progression (in addition to biochemical progression).
  • The 8-year overall survival rate was 88 percent.
  • No patient has died of prostate cancer or related toxicities.
  • 3 patients experienced late-stage Grade 3 genitourinary toxicities.
  • No Grade 4 or Grade 5 toxicities were observed.

The authors conclude that:

  • This type of trial can be successfully completed in the cooperative group setting.
  • The clinical outcomes of this trial of iodine-125 brachytherapy “compare very favorably with other brachytherapy published series as well as with surgical and external beam radiotherapy series.”
  • The prospective, multi-center design of this study suggests that the outcomes of this trial could reasonably be expected in a “real world” setting.

Earlier reports from this trial (e.g., the article by Gillin et al. in 2005) have indicated some additional learnings from this study, such as the need for a central review process of radiation dose-volume analysis within the cooperative group setting.

One Response

  1. These results are helpful in roughly estimating the difference in success between centers of excellence and more community-based brachytherapy results.

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