The Cyberknife System and Prostate Cancer: Research Demonstrates a Positive Impact on Toxicities, Biochemical Survival, and PSA

Ariana Gopal

The objective of this week’s paper is to evaluate the effects of the Cyberknife system on a specific type of cancer.  Literature reviewed in the past, specifically on cancers effecting the nervous system, indicated that the use of the Cyberknife for cancer treatment should extend to various types of cancers, such as those of the lung or prostate.  The impact of the Cyberknife system on prostate cancer was specifically evaluated in this assignment.

One of the main concerns that comes with performing radiosurgery on cancer patients is the fact that an incredibly high dose of radiation sent to a target area can negatively impact the normal tissues and organs that surround that area.  In the case of prostate cancer, these sensitive organs could be the rectum and/or the bladder. One of the articles this week specifically discussed the feasibility of using the Cyberknife to target the prostate while leaving the healthy, sensitive tissues surrounding it unharmed (King et al., 2003).  It was mentioned that the Cyberknife system is able to track daily position changes made by the patient during radiation delivery and ultimately correct or this (King et al., 2003).  The system’s ability to correct for this comes from gold “seeds,” or fiducial markers placed within the prostate gland trans-rectally via a urologist (King et al., 2003).  This is what ultimately makes it feasible to deliver a high dose of radiation to a target area while sparing the healthy surrounding tissues, supporting the accuracy of the system (King et al., 2003).

Figure 1: Representative treatment plans (axial and coronal views) from a patient to be treated with the Cyberknife system. Tumor coverage is 95%. (Friedland et al., 2009)

Numerous articles discussing the treatment of prostate cancer with the Cyberknife have been published since the theoretical accuracy of the system has been established.  For example, a study conducted in 2015 sought to evaluate the biochemical disease-free survival and impact of Cyberknife treatment on PSA levels for 437 patients with prostate cancer (Davis et al., 2015).  Genitourinary and gastrointestinal toxicities reports were minimal in the patient population (Davis et al., 2015).  Median PSA decreased from 5.8 ng/mL to 0.88, 0.4, and 0.3 at 1, 2, and 3 years post treatment (Davis et al., 2015).  Two-year biochemical disease-free survival was considered significant at 96.1% (Davis et al., 2015).

Additional research conducted in this field has shown that patients treated with the Cyberknife for prostate cancer experienced low grade toxicities, and a biochemical recurrence rate of 20%, none of which were patients at low or intermediate risk (Koh et al., 2014).  Additionally, research performed in 2009 reported that 82% of patients with prostate cancer and treated by the Cyberknife maintained their sexual functioning post treatment (Friedland et al., 2009).  Lastly, in a study evaluating the clinical outcomes of the Cyberknife system on low and intermediate risk prostate cancer at a median of 51 months post treatment, no biochemical failures were reported, and most toxicities returned to baseline after a follow up of 2 months, none of which were reported as grade 3 genitourinary and gastrointestinal toxicities (Kim et al., 2016).

As demonstrated in the research above, the Cyberknife system demonstrates a positive impact on reducing PSA, having a high correspondence to biochemical disease-free survival, and maintaining sexual function.  Although toxicities did exist among the various patient populations, a majority of them were considered low grade.  The research here clearly shows promise for the Cyberknife system with respect to the treatment of individuals with prostate cancer.

References

Davis, J., Sharma, S., Shumway, R., Perry, D., Bydder, S., Simpson, C. K., & D’ambrosio, D. (2015, December 04). Stereotactic Body Radiotherapy for Clinically Localized Prostate Cancer: Toxicity and Biochemical Disease-Free Outcomes from a Multi-Institutional Patient Registry. Cureus.

Friedland, J. L., Freeman, D. E., Masterson-Mcgary, M. E., & Spellberg, D. M. (2009, October). Stereotactic Body Radiotherapy: An Emerging Treatment Approach for Localized Prostate Cancer. Technology in Cancer Research & Treatment, 8(5), 387-392.

Kim, H. J., Phak, J. H., & Kim, W. C. (2016, June 17). Hypofractionated stereotactic body radiotherapy in low- and intermediate-risk prostate carcinoma. Radiation Oncology Journal Radiat Oncol J.

King, C. R., Lehmann, J., Adler, J. R., & Hai, J. (2003, February). CyberKnife Radiotherapy for Localized Prostate Cancer: Rationale and Technical Feasibility. Technology in Cancer Research & Treatment, 2(1), 25-29.

Koh, D., Kim, J., Kim, H., Chang, Y., & Kim, H. J. (2014, March). Clinical Outcomes of CyberKnife Radiotherapy in Prostate Cancer Patients: Short-term, Single-Center Experience. Korean Journal of Urology Korean J Urol, 55(3), 172-177.