Locally advanced or unfavorable disease
For patients who present with a prostate-specific antigen (PSA) level greater than 10 ng/ml, Gleason score > 7, palpably advanced tumor, or combinations of these factors, the prognosis may decrease dramatically compared with the “favorable” group, especially if multiple negative factors are present (29). As with early stage cases, there is a lack of consensus as to optimal therapeutic management.  High dose external beam plus or minus androgen suppressive therapy is commonly applied in such cases, which are often considered too advanced for small margin treatment approaches such as radical prostatectomy or brachytherapy. Combined modality radiation approaches are also used, for example - external beam radiotherapy (EBRT) plus HDR brachytherapy, calling upon their complementary strengths, to treat both the central disease and potential cancer spread beyond the prostate as effectively as possible (14).

CyberKnife® prostate radiosurgery would qualify as a small margin approach, and therefore, not suitable for use against non-favorable cases as monotherapy. The combination of EBRT plus a CyberKnife® prostate boost may be a much more viable approach to these patients though, theoretically delivering identical efficacy compared with combined EBRT plus HDR brachytherapy, which has been published effective for non-favorable patients (14).

EBRT + CyberKnife® provides comparable radiation coverage and biologic effectiveness compared with EBRT plus HDR brachytherapy and as such, is reasonably delivered in routine clinical practice, whether or not the subject of a clinical trial. CyberKnife® radiosurgery delivers the benefit of recapitulating HDR brachytherapy radiation dose sculpting without the hospitalization and without the indwelling tubes.