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Keywords:

  • Cyberknife®;
  • stereotactic body radiation therapy;
  • hypofractionated radiation therapy;
  • prostate cancer

Objectives

  • To describe the most recent data from phase I and II clinical trials of stereotactic body radiation therapy (SBRT) using image-guided robotic radiosurgery, specifically the Cyberknife® (Accuracy Incorporated, Sunnyvale, CA, USA).
  • To better determine thecurrent role of this type of radiosurgery in prostate cancer (PCa) management.

Materials and Methods

  • Current clinical trials and relevant retrospective studies were identified from the literature, clinical trial databases, websites and conference abstracts.
  • The indications, technical aspects, efficacy and toxicity of SBRT using the Cyberknife® system were summarized.

Results

  • The Cyberknife® system is an experimental treatment mostly used for localized PCa in stage cT1/T2a–b N0 M0 with a Gleason score ≤7 and PSA level ≤20 ng/mL. Hypofractionated radiation therapy was delivered in five fractions of 7–7.25 Gy for a total dose of 35–36.25 Gy.
  • After treatment, the median PSA levelfell from 4.9–8.3 ng/mL to 0.1–1.6 ng/mL at a median follow-up of 4–60 months.
  • The biochemical progression-free survival rates ranged from 78.3 to 100%.
  • Acute and late toxicities were mostly grade 1/2 rectal or urinary complications. Few grade 3 and no grade 4 toxicities occurred during follow-up; however, erectile dysfunction and testes toxicity were also reported.

Conclusions

  • The use of the Cyberknife® system is limited mainly by its pretreatment and maintenance costs.
  • Despite encouraging preliminary results, longer-term follow-up and randomized controlled phase III clinical trials are necessary before the Cyberknife® system becomes a standard treatment method.