Stereotactic body radiation therapy cures nearly 99 percent of prostate cancer patients in 5-year trial

Stereotactic body radiation therapy (SBRT) to treat prostate cancer showed a 5-year cure rate of 98.6% in a clinical trial, according to a study published April 18, 2016 in European Journal of Cancer.

“The high cure rate is striking when compared to the reported 5-year cure rates from other approaches like surgery or conventional radiation, which range between 80% to 90%, while the side effects of this treatment are comparable to other types of treatment,” said the study’s lead author Raquibul Hannan, MD, PhD, Assistant Professor of Radiation Oncology at the University of Texas Southwestern Medical Center’s Harold C. Simmons Comprehensive Cancer Center, in Dallas, TX.

SBRT involves multiple beams of high-dose radiation coordinated at different angles to precisely target tumors. Compared to conventional external beam radiation, which requires daily doses over multiple weeks, SBRT requires just a few visits.

“SBRT is both more convenient and has increased potency,” said senior author Robert Timmerman, MD, Director of the Annette Simmons Stereotactic Treatment Center at UT Southwestern, and Professor and Vice Chairman of the Department of Radiation Oncology. 

“The current form of radiation is 44 treatments given over 9 weeks,” he explained. “In contrast, the SBRT therapy we used allows the delivery of highly focused radiation in only 5 treatments, allowing patients to return to their normal lives more quickly.”

The multi-institutional clinical trial involved 91 patients diagnosed with stage I or stage II prostate cancer. Patients were grouped into cohorts to receive different doses of radiation—a total of either 45, 47.5, or 50 Gray (Gy)—delivered in 5 treatment sessions.

After 5 years of follow-up, only one patient had a recurrence of his cancer. Five-year overall survival was 89.7%, although no deaths were due to prostate cancer or the treatment. Also, no patients developed distant metastases.

In addition to a higher cure rate and fewer treatments, SBRT treatment also showed a side effect profile that is not much different than other forms of prostate cancer treatment. However, about 25% of patients developed erectile dysfunction, which is fewer than with conventional radiation or surgery, Dr. Hannan said. Patients also had a small risk of longer-term urinary and rectal complications, but these too are comparable to conventional treatments.

The study showed that the lower doses of SBRT—45 Gy and 47.5 Gy—resulted in acceptable toxicity, but patients who received doses of 50 Gy had higher rates of late toxicity.

“Future studies will clarify the dose necessary to achieve appropriate balance between control and toxicity,” the authors wrote. Further research will also determine whether SBRT will be accepted as a standard of care, they added.

For now, UT Southwestern researchers are preparing to investigate SBRT for high-risk, stage III prostate cancer patients. “Our hope is that the high potency of this form of treatment will significantly improve treatment of these patients,” said Dr. Hannan, the principal investigator of the trial.