For a man with localized prostate cancer (clinical stage T1‑T2, Gleason score ≤7, PSA ≤20 ng/mL) and a life expectancy of at least 10 years, is CyberKnife stereotactic body radiotherapy an appropriate treatment option?

CyberKnife for Localized Prostate Cancer: Not a Standard Treatment Option

CyberKnife stereotactic body radiotherapy (SBRT) is not recommended as a standard treatment option for localized prostate cancer, as it lacks high-quality comparative evidence demonstrating equivalent oncological outcomes to established therapies. 1

Guideline Position on Focal Ablative Therapies Including CyberKnife

The European Association of Urology conducted a comprehensive systematic review in 2021 specifically addressing focal ablative therapies (including focal external beam radiotherapy such as CyberKnife) for localized prostate cancer. 1 Their conclusions are unequivocal:

• The certainty of evidence regarding comparative effectiveness of focal therapies as primary treatment for localized prostate cancer was low, with significant uncertainties. 1
• Focal therapies should ideally be performed within clinical trials or well-designed prospective cohort studies until higher certainty evidence emerges. 1
• There was no strong evidence showing that focal therapies compare favorably with standard treatments; consequently, focal therapy is not recommended for routine standard practice. 1

Standard Treatment Options for Your Clinical Scenario

For a man with intermediate-risk localized prostate cancer (T1-T2, Gleason ≤7, PSA ≤20 ng/mL) and life expectancy ≥10 years, the established treatment options are: 1

First-Line Standard Options:

• Radical prostatectomy with pelvic lymph node dissection (if predicted probability of lymph node metastasis ≥2%) 1
• External beam radiation therapy (3D-CRT/IMRT with daily image guidance) with or without 4-6 months of androgen deprivation therapy 1
• Brachytherapy (for selected patients without Gleason pattern 4 or 5) 1

Active Surveillance:

• Not recommended for patients with life expectancy >10 years and intermediate-risk disease 1

Why CyberKnife Is Not Standard

The fundamental problem with CyberKnife SBRT is the absence of high-quality comparative data:

• No randomized controlled trials comparing CyberKnife to radical prostatectomy or conventional external beam radiation therapy exist 1
• The available studies are small, retrospective case series with short follow-up and no comparison groups 2, 3, 4, 5
• Long-term oncological outcomes (10-15 years) are unknown, which is critical for a disease where men may live decades after treatment 1

What the CyberKnife Research Actually Shows

The available CyberKnife studies demonstrate feasibility and short-term biochemical control, but have critical limitations:

• A 2011 Korean study of 44 patients showed 100% 5-year cause-specific survival, but median follow-up was only 40 months and there was no comparison group 2
• A 2016 study of 33 patients with median 51-month follow-up showed no biochemical failures, but again lacked any comparative arm 3
• A 2023 study of 122 patients showed 95.7% 5-year biochemical disease-free survival, but this is a single-arm study without comparison to standard treatments 4

These studies cannot answer whether CyberKnife is equivalent to, better than, or worse than radical prostatectomy or conventional radiation therapy for long-term cancer control and survival. 1

The Evidence-Based Treatment Algorithm

For intermediate-risk localized prostate cancer with life expectancy ≥10 years: 1, 6, 7

1. Discuss standard options: Radical prostatectomy vs. external beam radiation therapy (75.6-78 Gy) ± short-term ADT (4-6 months)
2. Consider patient factors: Baseline urinary/sexual function, comorbidities, patient preference
3. If radiation is chosen: Use conventional fractionation (75.6-78 Gy) or moderately hypofractionated regimens with established evidence, NOT ultra-hypofractionated SBRT like CyberKnife
4. If surgery is chosen: Ensure extended pelvic lymph node dissection if risk of nodal involvement ≥2%

Critical Caveats

• Brachytherapy monotherapy is contraindicated if there is any Gleason pattern 4 or 5 component, even in intermediate-risk disease 1
• Short-term ADT (4-6 months) with radiation is an option for intermediate-risk disease, but the evidence is strongest in mixed populations, not pure intermediate-risk cohorts 1
• Active surveillance is inappropriate for intermediate-risk disease with life expectancy >10 years 1

When Might CyberKnife Be Considered?

CyberKnife SBRT should only be offered: 1

• Within a clinical trial comparing it to standard treatments
• Within a well-designed prospective registry with long-term follow-up and standardized outcome reporting
• After thorough informed consent explaining the lack of comparative long-term data

The patient must understand that choosing CyberKnife means accepting unknown long-term cancer control rates compared to treatments with decades of follow-up data. 1