More than 93 percent of men with low risk-prostate cancer treated with the CyberKnife System were still disease-free 10 years later, said the system’s manufacturer, Sunnyvale, California-based Accuray.

A study detailing the treatment, “Stereotactic Body Radiotherapy for Low-Risk Prostate Cancer: A Ten-Year Analysis,” appeared in the journal Cureus.

CyberKnife edlivers stereotactic body radiation therapy (SBRT), a type of radiotherapy that uses special equipment to position a patient and precisely deliver radiation to tumors in the body. The prostate gland can move unpredictably during the course of treatment, and accurately tracking its position and correct radiation delivery site is of utmost importance.

CyberKnife treatment involves five daily sessions, unlike conventional radiotherapy, which requires 30 to 40 sessions.

Last February, Accuray reported that 100 percent of men with low-risk prostate cancer given CyberKnife radiation therapy were still disease-free after seven years, as were 88.5 percent of men at intermediate risk.

In the latest study, 230 men with low-risk prostate cancer were treated with the CyberKnife System and monitored for a median follow-up of nine years. The median age was 69.5 years. Ten years later, 98.4 percent of these men had not seen their disease progress throughout the study, and 93.7 percent had no cancer signs or symptoms at all.

PSA levels help doctors diagnose prostate cancer, with high levels usually meaning that the disease has returned or spread to distant regions. While PSA levels at baseline averaged 5.6 ng/ml among the study’s participants, they had dropped to an average 0.1 ng/ml within five years and have remained at this low level ever since.

Bowel and urinary function initially declined after treatment, according to a patient-reported questionnaire, but those scores returned to baseline and remained there through the remainder of the study. Scores on sexual function, however, declined by 40 percent.

“This is a groundbreaking study — the first to report on the efficacy and toxicity of SBRT in the treatment of low-risk prostate cancer following 10 years of treatment,” Dr. Alan Katz of New York’s Flushing Radiation Oncology said in a press release. “The study outcomes were excellent both in terms of disease control and tolerability, and were superior to long-term conventional intensity-modulated radiation therapy, based on results from other studies.”

Fabienne Hirigoyenberry-Lanson, Accuray’s vice-president of global medical and scientific affairs, added that following early-stage prostate cancer diagnosis, men now have a variety of treatment options from which to choose.

“CyberKnife prostate SBRT is increasingly being selected by men with low- or intermediate-risk disease who opt for treatment with radiation therapy,” she said. “This new CyberKnife research adds to the most extensive compendium of published prostate SBRT studies available in the industry. The data continue to validate this precise and accurate approach to the treatment of prostate cancer which offers minimal disruption to patients’ daily lives.”