'Cyberknife' Radiation for Prostate Cancer: 5-Year Results Still Leave Questions

5-Year Results Still Leave Questions

Gerald Chodak, MD


February 22, 2011

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Hello. I'm Dr. Gerald Chodak from Medscape. This week I want to talk about stereotactic radiation using the CyberKnife® (Accuray Inc., Sunnyvale, California) system, a treatment that has been in use for several years although long-term results are not yet available. The authors reported a study[1] of 41 patients treated at UCLA Medical Center and Naples, Florida. The patients have been followed for about 5 years, and the results were analyzed in terms of biochemical disease-free survival using the Phoenix definition.

The authors claim that the results are comparable to those with other forms of treatment when looking at 5-year biochemical disease-free survival. They also looked at quality of life measurements, although they did not report any information about impact on sexual function. Their results, they claim, are similar to other studies in terms of safety.

Having stereotactic radiation certainly could be a significant benefit to patients in terms of convenience and also in cost. The treatment takes much less time than standard radiotherapy using intensity-modulated radiation therapy. But the question we need to ask ourselves at this time is: How much information do we have to tell patients and what can we tell them about the long-term effectiveness of this therapy? While I applaud the new information, the problem I continue to believe is that it's just too early to really know what to tell patients. Five years of results in a series of 41 patients treated for low-risk disease means very little. We know that many of those men don't need to be treated at all, so the fact that the biochemical disease-free survival is similar to that with surgery and other forms of radiation is interesting, but it's not enough at this time to say that it is a comparable treatment.

Now that doesn't mean it shouldn't be offered to patients. But I still believe that, at this time, it's not possible to say that it is an equivalent therapy with similar long-term survival. After all, long-term survival is really the outcome that matters most, particularly for men who have low-risk prostate cancer.

Another question that I wonder about is why no information was provided about sexual function. That certainly is a critical piece of information that patients need to know, and although measurements were made, that analysis was left out of the report.

I think the information or the bottom line, for now, is that this has the potential to be a very important modality to offer to men with prostate cancer, particularly with low-risk disease, providing that long-term results prove to be equitable. Should men be offered this treatment and told that it's equivalent treatment at this time? The answer is no. This does not permit that kind of conclusion, but it certainly is something reasonable to discuss and make sure that patients understand its current limitation and also its potential. I welcome your comments. Thank you.


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