For selected patients with localised prostate cancer, CyberKnife enables high-precision stereotactic body radiotherapy (SBRT), usually delivered in five outpatient sessions without surgery or general anaesthesia. ERCM Munich has more than 20 years of experience in robotic radiosurgery and has treated more than 1,000 patients with prostate cancer.
According to current scientific understanding, prostate cancer is not caused by a single factor, but develops through the interaction of several factors. Age is a major risk factor. Prostate cancer is rare before the age of 50, while its incidence rises markedly from approximately 65 years of age.
Age-related changes and genetic damage accumulated in prostate cells over decades make a substantial contribution to tumour development.
Genetic predisposition also plays an important role. Men whose father or brother has been affected have an increased risk of developing the disease. Inherited variants in genes including BRCA1, BRCA2, ATM and CHEK2 may increase the risk further. Approximately 5-15% of prostate cancers are considered to have a pronounced hereditary component.
The growth of the prostate and of many prostate cancers is also androgen-dependent. However, testosterone should not be regarded as the sole cause. Lifestyle factors such as obesity and physical inactivity are also discussed as possible contributory factors, although their influence is smaller and less clearly established than that of age and genetic predisposition.
For recurrent prostate cancer: see
prostate cancer recurrence
CyberKnife is the name of an image-guided, robotic radiotherapy system. The underlying medical treatment technique is known as stereotactic body radiotherapy (SBRT). A compact linear accelerator is mounted on a mobile robotic arm and can direct radiation towards the target from 1,800 different directions.
When treating the prostate, small radiopaque markers known as fiducial markers are used as reference points. During irradiation, the position of the prostate is repeatedly verified using image guidance. If the system detects a change in position, the beam alignment can be adjusted. This form of image-guided robotic tracking is possible only with CyberKnife technology and reduces radiation exposure to surrounding organs such as the bladder and bowel. Image guidance is particularly relevant for the prostate because its position can change during treatment, for example as rectal or bladder filling varies.
CyberKnife treatment is considered particularly for patients with localised prostate cancer. However, whether stereotactic radiotherapy is appropriate does not depend on the Gleason score alone.
SBRT has been particularly well studied in localised tumours with a low- or intermediate-risk profile. In low-risk prostate cancer, however, it must first be determined whether immediate treatment is required at all or whether active surveillance would be more appropriate.
For higher-risk disease, treatment decisions are more complex and may require a combination of different treatment modalities, including androgen-deprivation therapy.
Early-stage prostate cancer is frequently asymptomatic and is often detected through an elevated prostate-specific antigen (PSA) level or during preventive assessment. With increasing local tumor burden or advanced disease, clinical symptoms may develop:
Many of these symptoms are nonspecific and may also occur in benign prostatic hyperplasia or inflammatory conditions. Further diagnostic evaluation is therefore required to establish or exclude malignancy.
The diagnosis and staging of prostate cancer are based on the integrated assessment of clinical findings, laboratory parameters, imaging, and histopathological examination.
An elevated serum PSA level is a common initial finding prompting further evaluation. Prostate-specific antigen is a serine protease produced by prostatic epithelial cells. Elevated PSA concentrations may occur in prostate cancer but are not cancer-specific and may also be seen in benign prostatic hyperplasia, prostatitis, urinary retention, or following manipulation of the prostate. Interpretation therefore includes not only the absolute PSA concentration but also PSA kinetics, clinical context, prostate volume, and, where appropriate, PSA density.
Digital rectal examination (DRE) is generally performed as part of the clinical assessment. The posterior surface of the prostate is palpated through the rectum to identify induration, nodularity, asymmetry, or other findings suspicious for malignancy. MRI When clinically significant prostate cancer remains suspected, multiparametric magnetic resonance imaging (mpMRI) of the prostate is now a central component of the diagnostic pathway. mpMRI provides high-resolution anatomical and functional assessment of suspicious intraprostatic lesions and supports targeted biopsy planning.
PI-RADS is a standardized reporting and assessment system for prostate mpMRI. It provides a structured estimate of the likelihood that an imaging abnormality represents clinically significant prostate cancer.
Definitive diagnosis requires histopathological confirmation by prostate biopsy. Multiple tissue cores are obtained, increasingly via a transperineal approach, with MRI-targeted sampling of suspicious lesions frequently combined with systematic biopsy. Microscopic demonstration of malignant prostatic epithelial cells establishes the diagnosis.
Histopathological assessment provides essential information regarding tumor differentiation and biological aggressiveness. The Gleason grading system and the corresponding ISUP Grade Groups are central to risk stratification. The Gleason score reflects the architectural differentiation of prostate adenocarcinoma compared with normal prostatic glandular tissue. The pathologist identifies the predominant and second most prevalent growth patterns. These are reported separately, with the predominant pattern first.
Although both combinations yield a total Gleason score of 7, their biological behavior differs:
Gleason patterns historically range from 1 to 5; in contemporary diagnostic practice, prostate carcinoma is predominantly assigned patterns 3, 4, and 5.
Gleason score 6 (3 + 3) is the lowest score routinely assigned to prostate adenocarcinoma in current practice and corresponds to ISUP Grade Group 1. Gleason score 7 represents intermediate-grade disease, with the distinction between 3 + 4 and 4 + 3 being clinically important. Gleason scores 8–10 correspond to high-grade disease with an increased risk of local progression, metastatic dissemination, and prostate-cancer-specific mortality.
Tumor extent is additionally classified according to the TNM system:
Additional staging investigations may include:
Bone scintigraphy, particularly when osseous metastatic disease is suspected Treatment decisions integrate multiple prognostic and patient-related factors:
The most appropriate treatment depends primarily on tumour stage, PSA level, Gleason score, age, comorbidities and the patient's personal priorities. For localised prostate cancer, both radical prostatectomy and modern radiotherapy techniques are established curative treatment options.
Surgery removes the prostate completely, but involves an operation and may have consequences such as urinary incontinence or impaired sexual function.
Conventional external-beam radiotherapy treats the prostate without surgery, but generally requires more treatment sessions and may be combined with hormone therapy, depending on the risk profile.
CyberKnife treatment, by contrast, is a highly precise form of stereotactic radiotherapy that can be delivered to suitable patients on an outpatient basis, without anaesthesia and in only a few sessions. It is a potential treatment option particularly for localised low- or intermediate-risk tumours.
The decisive question is therefore not which procedure is fundamentally 'better', but which treatment offers the best balance of prospects for cure, side effects and preservation of quality of life for the individual tumour situation.
| Criterion | Surgery | Conventional radiotherapy | CyberKnife |
|---|---|---|---|
| Tumour size / stage | Localised disease, all risk groups | Localised to locally advanced disease | Localised disease (Gleason score ≤ 7, PSA < 20 ng/mL) |
| Prostate volume | Regardless of prostate volume | Regardless of prostate volume | < 80 cm³ |
| Symptoms | Also suitable for patients with significant symptoms | Also suitable for patients with significant symptoms | Mild to moderate symptoms |
| Treatment aim | Surgical removal of the tumour | Destruction of tumour cells | Destruction of tumour cells |
| Hospital admission | Required | Not required | Not required |
| Treatment duration | Surgical procedure lasting several hours | Approximately 20-40 treatment sessions over 4-8 weeks | 3-5 treatment sessions over 1-2 weeks |
| Long-term tumour control | 90% | 90% | 90% |
| Return to daily activities | Recovery period of several weeks | Treatment course extending over several weeks | Immediate |
Several treatments with curative intent are available for localised prostate cancer. These include surgery and modern forms of radiotherapy in particular.
Randomised long-term data are now available for stereotactic radiotherapy.
In the international phase III PACE-B trial, five-fraction SBRT in patients with localised low- to intermediate-risk prostate cancer was non-inferior to conventional or moderately hypofractionated radiotherapy with regard to biochemical or clinical treatment failure.
The current German S3 guideline now explicitly includes extreme hypofractionation as a treatment option for selected patients. At the same time, it emphasises that potential genitourinary side effects and the patient's individual baseline status must also be considered when treatment is selected.
ERCM also participated in the prospective German HYPOSTAT study. This multicentre phase II study investigated robotic CyberKnife SBRT for localised prostate cancer. The final analysis demonstrated a favourable short-term toxicity profile for treatment with 35 Gy in five fractions.
CyberKnife treatment of the prostate is a highly precise form of stereotactic body radiotherapy (SBRT). It is generally well tolerated and is delivered on an outpatient basis without surgery or general anaesthesia. Nevertheless, as with any form of radiotherapy, side effects may occur.
The most common effects are temporary irritation of the urinary tract or rectum. Severe or persistently disabling side effects are uncommon overall.
During treatment or in the first days and weeks afterwards, urinary symptoms may occur in particular. These include:
These symptoms result from temporary irritation and swelling of the prostate and urethra.
They resolve in most patients and can be treated with medication if necessary.
Temporary bowel symptoms occur less frequently, for example:
Some patients also report temporary fatigue. Many patients are able to continue their normal daily activities to a large extent during and immediately after the treatment course.
Marked new-onset urinary incontinence is relatively uncommon following primary stereotactic radiotherapy of the prostate. Unlike surgery, the prostate and urinary sphincter are not surgically removed or divided. Temporary changes in urination may nevertheless occur. The individual risk depends, among other factors, on pre-existing urinary symptoms, prostate size, previous prostate procedures and other comorbidities.
Following prostate treatment, erectile function may decline over the subsequent years. Unlike some acute symptoms, this change often does not occur immediately after treatment. The individual risk depends substantially on erectile function before treatment, age, vascular and metabolic disease, and whether additional androgen-deprivation therapy is required.Impaired sexual function therefore cannot be excluded completely, even with highly precise CyberKnife treatment.
Some side effects may not develop until months or years after radiotherapy. Possible late effects include:
Severe late effects involving the bladder or bowel are very rare, but cannot be excluded completely.
During CyberKnife treatment, the position of the prostate is repeatedly verified by image guidance using implanted markers. Changes in prostate position can be detected and taken into account when aligning the radiation beam. This allows the radiation dose to be focused very precisely on the planned target volume while keeping exposure of adjacent structures such as the rectum and bladder as low as possible. Before each course of treatment, physicians and medical physicists prepare an individual radiotherapy plan.
Prostate cancer can vary in aggressiveness. The histological characteristics and size of the tumour, together with its extension into surrounding structures, are key determinants of prognosis.
Some prostate cancers grow slowly and therefore do not necessarily require immediate surgery or treatment.
These tumours are monitored closely. Other tumours are more aggressive, such as those with a Gleason score of 9 or 10, and generally require prompt treatment because their tumour biology may allow them to metastasise rapidly.
By definition, prostate cancer is malignant. Tumour biology and local extent determine treatment and prognosis.
CyberKnife treatment of prostate cancer is usually delivered in five treatment sessions on consecutive treatment days; three sessions may be planned in selected cases. Each session generally lasts approximately 30 minutes and is performed on an outpatient, non-invasive basis.
The most appropriate treatment depends primarily on tumour stage, risk profile, age and individual comorbidities. Surgery removes the prostate completely, but involves an operation and may result in urinary incontinence or erectile dysfunction. Conventional external-beam radiotherapy also avoids surgery, but generally requires multiple treatment appointments over several weeks.
For suitable patients, stereotactic radiosurgery with CyberKnife enables highly precise, non-invasive treatment, usually in only five sessions, without surgery or general anaesthesia.
For localised prostate cancer, all three approaches can provide effective treatment. The method best suited to the individual patient should be determined on the basis of tumour findings and the patient's personal circumstances.
The frequently expressed claim that surgery is categorically no longer possible after CyberKnife treatment of the prostate is incorrect. If a recurrence following CyberKnife treatment remains confined to the prostate, salvage prostatectomy may be considered in carefully selected patients. This involves surgical removal of the prostate after previous radiotherapy.
Such an operation is, however, more challenging than primary prostatectomy. Previous treatment may cause tissue changes and scarring, making surgery more difficult and potentially increasing the risk of urinary incontinence, erectile dysfunction and other surgical complications in particular.
Salvage prostatectomy should therefore be performed at a centre with appropriate experience. In addition to surgery, further local treatment options are now available for localised recurrence, depending on the findings, tumour biology and previous treatment.
The appropriate treatment for recurrence is determined individually on the basis of the PSA trajectory, modern imaging, repeat biopsy where appropriate, and the patient's general health.
Acute symptoms typically occur shortly after treatment or within the first few weeks. Urinary symptoms may temporarily increase at first and then subside. The course varies between individuals.
CyberKnife irradiation itself is painless. Irritative urinary or rectal symptoms may occur in the days or weeks after treatment.
Many patients are able to continue their normal daily activities to a large extent during and after the outpatient treatment course. Whether and when more strenuous physical activity is appropriate depends on the individual situation and any symptoms that arise.
Erectile dysfunction may occur after any form of prostate radiotherapy. The risk often develops over several years and depends strongly on age, baseline function and comorbidities. Long-term preservation of potency therefore cannot be guaranteed.
Marked new-onset incontinence is very rare following primary prostate SBRT. Temporary urinary urgency, increased urinary frequency or a weaker urinary stream occur more commonly.
An individual's risk of side effects cannot be predicted from the diagnosis of prostate cancer alone. Relevant factors include prostate volume, pre-existing urinary symptoms, previous surgery, age, comorbidities and the individual radiotherapy plan. Before CyberKnife treatment at ERCM, the available findings are therefore reviewed and the potential benefits and risks of treatment are discussed individually with the patient.
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