SBRT for Prostate Cancer Correlated With Higher Cure Rates Than Standard of Care in 5-Year Study
Increased doses created severe late toxicity, and more research is needed to make stereotactic body radiation therapy a standard of care.
Stereotactic body radiation therapy (SBRT) to treat prostate cancer may provide higher cure rates than more traditional approaches, according to a study from the University of Texas Southwestern Medical Center (UTSW) in Dallas.1 The researchers found that SBRT resulted in excellent biochemical control rates at 5 years but that doses greater than 47.5 Gy in 5 fractions led to increased severe late toxicity.
“This noninvasive, effective, convenient, and relatively safe treatment option is the future of prostate cancer treatment, and making patients and their care providers aware of the findings of this and other related studies is going to be crucial,” said lead study author Raquibul Hannan, MD, PhD, assistant professor of radiation oncology at UT Southwestern Medical Center and member of the Harold C. Simmons Comprehensive Cancer Center in Dallas, TX.
This clinical trial is the first to publish 5-year results of SBRT treatment for prostate cancer. A total of 91 patients were included in the analysis, and 63.7% had National Comprehensive Cancer Network intermediate-risk disease and 36.3% had low-risk disease. The researchers found that freedom from biochemical failure was 100% at 3 years and 98.6% at 5 years. The median follow-up was 54 months, and the actuarial distant metastasis-free survival was 100% at 3 and 5 years. Out of all the patients, only 1 failed (1.4%).
“When we examined this 1 patient carefully, we realized that the failure was outside the radiation field, so this suggests that SBRT likely did its job of killing the cancer, but the cancer had probably already metastasized outside the radiation field,” Dr Hannan told Cancer Therapy Advisor.
The study showed 0% acute grade 3 or higher toxicity and 5.5% late urinary grade 3 or higher toxicity. Gastrointestinal acute toxicity of grade 3 or higher occurred in 2% of patients, and late toxicity of grade 3 or higher occurred in 7% of patients. The researchers reported that 4 men experienced grade 4 toxicity. Dr Hannan said decrease in erectile function was seen in 25% of patients, which is fewer than with conventional radiation or surgery.
To reduce the side effects associated with SBRT, ongoing clinical trials at UTSW are using a unique biodegradable rectal spacer gel to protect the rectum. Patients are also able to undergo many fewer treatments than with traditional therapies.
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“Benefits in addition to having only 5 treatments rather than 44 include increased patient convenience, which sometimes translates into feasibility,” said Dr Hannan. “Some patients that are coming in from remote locations would not have been able to receive this treatment if it had not been given in 5 fractions.”