Early results suggest a radiation therapy technique that delivers higher doses in fewer fractions could be a "viable alternative" for men with prostate cancer, according to research shared at ASTRO 2012 in Boston on Tuesday.

The technique promises dramatically shorter treatment times and possible cost savings for payers, but at least one expert warned that the study did not follow patients for very long and that rigorous, longer-term studies were needed.

In the study, researchers from institutions across the country pooling their patient data together found that stereotactic body radiation therapy using the CyberKnife in men with prostate cancer resulted in low rates of disease recurrence a median of three years later. And these rates were possibly lower than with some rival methods, although data from a randomized study are needed in the future, the report's author said.

"This statistic should encourage men to seek SBRT as a viable alternative" to surgery or other radiation treatments, such as brachytherapy and intensity-modulated radiation therapy, author Dr. Alan J. Katz, a radiation oncologist with Flushing Radiation Oncology in Flushing, N.Y., told reporters on a call Tuesday.

The study pooled data on 1,101 patients from Katz's own clinic, as well as eight other facilities, including Swedish Medical Center in Seattle, Beth Israel Deaconess Hospital in Boston, Georgetown University Hospital in Washington, D.C., and UCLA Medical Center in Los Angeles.

The patients were treated with the CyberKnife system, which delivers doses within small margins and performs real-time tracking using fiduciary markers, Katz said. Patients received 35-40 Gy in four to five fractions, many fewer than the 45 or more fractions patients usually get during IMRT schedules, he said.

Patients were then followed for a median 36 months, and close to half were followed for at least four years, according to a slide shown during Katz's presentation.

Katz said actuarial five-year disease-free survival, as measured by rising prostate-specific antigen levels, were 95 percent of low-risk patients, 90 percent for intermediate-risk patients and 80 percent of high-risk patients.

He said these results compared favorably with IMRT, the dominant radiation therapy technique, and added evidence to the view that prostate cancer is sensitive to dose per fraction and higher doses give better results.

"So far all the data we've seen support this," he said.

Interestingly, nearly 150 men in the study received antigen deprivation therapy to reduce testosterone levels, but this treatment had no influence on their outcomes, Katz said.

One exciting aspect of SBRT is because it is done in fewer fractions, it is less expensive for a payer like Medicare than IMRT, which can cost the government program upwards of $40,000 for a full round of treatments, at least in some areas, Katz said. Also, it only takes a few days to deliver treatment, instead of several weeks.

However, while praising the "cutting-edge" research, an expert warned that the patient follow-up time was too short to reach definitive conclusions and that more research was needed to make sure similar outcomes could be reached by other doctors.

"The follow up is relatively short," Dr. Colleen Lawson, ASTRO's new president, said on the call. "The devil's in the details. We've got to be sure to follow these patients long enough."

On the press call, Katz agreed that longer-term studies were needed but said he has data on some patients seven years out who still have good results and no new toxicities, which he said are generally seen in the first three years.

"I think these results will hold up over time, and I think at this point this should be a treatment that should be strongly considered," he said.

Since being approved to treat tumors all over the body by the Food and Drug Administration nearly 11 years ago, the CyberKnife is mostly used for lung, spine and liver tumors, according to the results of a survey cited by Radiology Today in an article last year.

The abstract is “Five-year Biochemical Control Rates for Stereotactic Body Radiotherapy for Organ Confined Prostate Cancer: A Multi-institutional Pooled Analysis.” Katz will present it Wednesday at ASTRO.

Katz reported having received honoraria from Accuray Inc., which makes the CyberKnife.