4- and 5-year outcomes after SBRT for localized prostate cancer

Two posters presented today at the Genitourinary Cancers Symposium have extended our knowledge about outcomes after stereotactic body radiation therapy (SBRT or CyberKnife therapy) for localized disease.

In the first of these two papers, Katz and Santoro have reported on the efficacy and toxicity of SBRT in a cohort of 50 patients with clinically organ-confined disease (T1cN0M0) followed for about 4 years.

In this cohort of patients:

  • 42 men had  low- and 8 intermediate-risk prostate cancer
  • All patients received 5 fractions of 7 Gy SBRT with Cyberknife to a total dose of 35 Gy delivered over 5 consecutive days.
  • Mean patient age was 69.5 years and mean pre-treatment PSA was 5.7 ng/ml.
  • All patients received 1,500 mg of amifostine intrarectally prior to each SBRT fraction.
  • Median follow-up was48 months (range, 46 to 53 months).
  • 1/50 patients has demnstrated biochemical failure and 3/50 patients died of intercurrent disease.
  • Median PSA at 48 months is 0.10 ng/ml (range, 0.01 to 3.5 ng/ml).
  • There have been no grade 3+ toxicities.
  • Actuarial 48 month rates for grade 2 genitourinary and rectal toxicity-free survival were 95.5 and 97.8 percent, respectively.
  • Of the 36 patients that were potent prior to treatment 29 (80.5 percent) have maintained potency.

In the second paper, Freeman and King report 5-year follow-up data from a pooled cohort of 41 patients followed at two centers for about 5 years. Their data show that:

  • 41 men received a prescribed dose of 35.0 to 36.25 Gy in five fractions.
  • No patient received hormone therapy.
  • The median follow-up was 5 years.
  • Biochemical progression-free survival was 93 percent.
  • All acute side effects resolved within 1 to 3 months of treatment completion.
  • There were no grade 4 toxicities, no late grade 3 rectal toxicity, and 1 patients with late grade 3 genitourinary toxicity after repeated urologic instrumentation. 

The available data from these two studies continue to show a high degree of effectiveness and safety of SBRT as a first-line treatment for localized, low- and intermediate-risk prostate cancer. It should be acknowledged that we will need 10-year and longer follow-up to fully appreciate the safety and effectiveness of this form of treatment, but the available data continue to be promising.

An additional poster presented at the symposium by Parthan et al. offers an Markov model-based analysis of the cost-effectiveness of SBRT as a first-line therapy for prostate cancer. This analysis suggests that SBRT is more expensive than surgery as a first-line therapy but significantly less expensive than intensity-modulated radiation therapy (IMRT) or proton beam radiation therapy (PBRT). It also suggests that SBRT is more cost-effective than surgery since patients tend to have a better quality of life post-treatment and lower lifetime costs associated with subsequent care. These are clearly preliminary data that will need further assessment over time.

3 Responses

  1. Thanks for reporting on this key QOL information with quite substantial follow-up, as well as the cost effectiveness comments.

  2. Wish I knew that 2 years ago.

  3. Very encouraging news.

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