Why Cyberknife

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Why Would Anyone Choose Cyberknife?

This is the title of an entry on the Prostate Cancer Blog, posted in May 2007 by Dr. Louis Potters, founder of the New York Prostate Institute.

Dr. Potters quotes an article in the International Journal of Radiation Oncology, Biology and Physics (vol. 67, No. 4, pp 1099) in which the author B.L. Madsen, MD writes,” … in a Phase I/II trial of SHARP (Stereotactic Hypofractionated Accurate Radiotherapy for localize prostate cancer) the actuarial 48-month biochemical freedom from relapse is 70% using the ASTRO definition.” Dr. Potters and many others know that these results are nowhere as good as the results widely reported with IMRT and seeds – with long-term (14 years and more) stats at this Center.

Without mincing words and pitting noted researchers against one another, the biggest obstacle facing Cyberknife (or Gammaknife or SHARP or any other such stereotactic hypofractionated therapy) for prostate cancer treatment is the lack of published clinical data to prove that it provides any better results than currently proven therapies. So why would anyone choose it?

Facilities and physicians promoting Cyberknife have big investments to recoup. The marketing machines are grinding out stories and material to glorify their products. “Cyber” is a sexy word in advertising buzz today. And, while the therapy has been successfully used with treating intracranial tumors for years, its application for soft tissue tumors (such as prostate) is glorified as “new” – as if everything “new” is “better.”

Website material from Accuray (manufacturer of the Cyberknife) touts its ability for clinical flexibility, delineation of tumor vs normal tissue for targeting, shorter treatment time and relatively low toxicity of the rectum and bladder.

But Beware!

A physician at a large CK facility in Oklahoma (who has threaten us not to use his name), in an internet patient support forum admits that “generally speaking, failure (at least in our hands)occurs most often when all our imaging does not make it possible to determine where the tumor stops and the normal tissue starts. We usually err on the side of including more volume, but sometimes we just can’t make the correct decision. We have sometimes been able to go back and re-treat the area we missed.”

The primary goal of combination therapy at Dattoli Cancer Center is to stop the identified tumor in its tracks, but the larger ultimate goal is to treat the entire gland. We know that whatever biochemical forces that were in place to cause the growth of the primary tumor are at work, albeit at a slower pace, throughout the gland. All the intense focal efforts to treat only the tumor is leaving the rest of the gland untouched – and ripe for future cancer growth.

With 4D IG-IMRT and DART and subsequent Palladium-103 brachytherapy, we are able to sculpt the radiation dose to surround the gland and spare the central core housing the urethra – attacking the active tumor cells and rendering the remainder of gland fallow for future tumor growth. It is our goal to have prostate cancer be a one-time event in the man’s life.

What Cyberknife Proponents Argue

Cyberknife proponents herald their 5-day treatment vs the 23 day IMRT program, as “more convenient” for the patient. How “convenient”, we ask, will it be for the patient to face a repeat performance 3, 4, 8 or more years down the road? Or how convenient will it be in the long run (late effects of radiation)when patients develop urethral and/or rectal fistulas, bladder damage, rectal ulcerations or perforations requiring colostomies, hip and bone necrosis – all documented complications from hypofractionated radiation?

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