Anova Cancer Care, in Colorado, recently announced that it has treated 1,500 prostate cancer patients using the CyberKnife System, a radiation therapy device designed to deliver stereotactic body radiation therapy (SBRT), an advanced form of high-dose radiation, directly to the tumor to minimize damage to nearby healthy tissue.

“We use the CyberKnife for prostate cancer because it offers distinct advantages when treating this disease; most notably it’s the only system available with the ability to track movement of the prostate and automatically adjust the radiation beam during treatment,” Lee K. McNeely, MD, radiation oncologist at Anova Cancer Care, said in a press release. “The CyberKnife System’s accuracy is sub-millimeter, enabling my colleagues and me to treat the disease with unparalleled preservation of healthy tissue and provide substantial quality of life and lifestyle benefits to patients.”

A study led by the device’s developer, Accuray, and presented at the 2017 Genitourinary Cancers Symposium  in February, demonstrated that 100 percent of men at low risk of prostate cancer given radiation therapy with the CyberKnife system were still disease-free after seven years, as were 88.5 percent of men at intermediate risk.

The study was based on the findings from a Phase 2 clinical trial (NCT02225262), which enrolled 259 prostate cancer patients — 112 of whom were low risk and 147 who were intermediate risk.

Three other studies, presented at the 36th European Society for Radiotherapy and Oncology (ESTRO) Annual Meeting in May,  showed that SBRT led to good long-term outcomes and low rates of severe toxicity in men with low- and intermediate-risk prostate cancer.  All three explored the long-term safety and efficacy of SBRT, which delivers high doses of radiation therapy to the tumor in a few fractioned radiation treatments (usually up to five), with high specificity to the tumor site, and two studies used the CyberKnife system.

The first, in Sweden, recruited 309 patients in 21 cancer centers to gather data on long-term treatment outcomes. The team found that only five patients experienced serious toxic effects, and treatment resulted in five-year survival rates in 95.6 percent of patients, and five-year disease-free survival in 97.1 percent of patients.

The second study, in Turkey, explored robotic SBRT using the CyberKnife system. The team at Hacettepe University compared different treatment approaches, in which radiation was given either sequentially or every other day. The rate of the so-called prostate-specific antigen bounce phenomenon, in which PSA levels transiently rise after radiotherapy, was also evaluated.

In total, 106 patients with low- and intermediate-risk cancer were enrolled and followed for a median of nearly five years.

The five-year biochemical relapse-free survival — deemed as a rise in PSA levels— in the group was seen to be 93.4 percent. Among the 16 percent of patients who experienced a PSA bounce, a slightly higher relapse-free survival rate was seen: 94.2 percent vs. 89 percent, respectively.

The third, in the Netherlands, compared SBRT to high-dose-rate brachytherapy, in which pieces of radioactive material are placed in or near a tumor. This study enrolled 329 low- and intermediate-risk cancer patients, with 206 receiving brachytherapy and 123 SBRT using CyberKnife. The median follow-up was 36 months, and patients were specifically screened for late side effects of the treatment.

Researchers found that only nighttime genitourinary toxicities were more common in the SBRT group, and rates of all other toxic effects were comparable in both groups.

The robotic CyberKnife system was specifically developed to track the movement of the prostate automatically, in real-time, throughout the entire therapeutic procedure, to allow for a noninvasive, more accurate and safe therapy. Treatment is typically completed within four or five sessions over the course of two weeks.

Accuray reports good feedback from patients due to the method’s convenience and reduced discomfort compared to conventional methods.

“The CyberKnife System is continuing to demonstrate its position as the radiation treatment of choice for more and more physicians and patients. It offers a convenient, noninvasive approach which precisely targets the prostate cancer with minimal disruption to patients’ daily lives,” said Joshua H. Levine, president and CEO of Accuray.