Single-dose radiotherapy appears safe, effective for intermediate-risk prostate cancer
Single-dose radiotherapy appeared safe and effective compared with hypofractionated stereotactic body radiotherapy among men with intermediate-risk prostate cancer, according to study findings published in JAMA Oncology.
“Ultra-high single-dose radiotherapy represents a potential alternative to curative extreme hypofractionated stereotactic body radiotherapy in organ-confined prostate cancer,” Carlo Greco, MD, researcher in the department of radiation oncology at Champalimaud Centre for the Unknown in Portugal, and colleagues wrote.
The researchers conducted the single-institution, randomized phase 2 PROSINT trial to assess the safety and feasibility of single-dose radiotherapy (SDRT) as a virtual prostatectomy approach compared with extreme hypofractionated SBRT among 30 men with organ-confined prostate cancer.
They randomly assigned the men to extreme hypofractionated SBRT (n = 15; median age, 66.3 years), delivered in five fractions of 9 Gy over 5 days, or 24 Gy SDRT (n = 15; median age, 73.6 years). Use of androgen deprivation therapy was prohibited.
Acute and late genitourinary and gastrointestinal physician-reported toxic effects and adverse events served as primary endpoints. Secondary endpoints included PSA response, PSA RFS and patient-reported quality of life as measured by the International Prostate Symptom Score (IPSS) and Expanded Prostate Cancer Index Composite-26 (EPIC-26) questionnaires.
Median follow-up was 48 months.
According to study results, both time to appearance and duration of acute and late toxic effects appeared similar across treatment groups. Researchers observed no differences in cumulative late actuarial urinary toxic effects (grade 1, HR = 0.41; 90% CI, 0.13-1.27; grade 2 or higher HR = 1.07; 90% CI, 0.21-5.57), similar actuarial grade 1 late gastrointestinal toxic effects (HR = 0.37; 90% CI, 0.07-1.94), and no grade 2 or higher late gastrointestinal effects.
Median 3-year PSA levels were 0.3 ng/mL (interquartile range [IQR], 0.1 ng/mL-0.59 ng/mL) with SBRT vs. 0.4 ng/mL (IQR, 0.3 ng/mL-0.48 ng/mL) with SDRT. Two men in the SBRT group and three in the SDRT group experienced PSA relapse at a median 26.6 months and 27.3 months. Among men with unfavorable-risk disease, actuarial 4-year PSA RFS rates were 75% with SBRT vs. 64% with SDRT (HR = 0.76; 90% CI, 0.17-3.31).
Researchers observed decreases in both groups in median summary EPIC-26 scores for genitourinary and gastrointestinal domains at 1 month, but both reverted to pretreatment scores by 3 months. In the SDRT group, 20% (90% CI, 3-37) of men experienced IPSS-derived transient late urinary fare symptoms between 9 months and 18 months.
“In this randomized clinical trial among patients with intermediate-risk prostate cancer, SDRT was safe and associated with low toxicity and the tumor control and quality-of-life endpoints closely match the SBRT arm outcomes,” Greco and colleagues wrote. “Further studies are encouraged to explore indications for SDRT in the cure for prostate cancer.”
Perspective
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Recently, there has been increased interest in making prostate cancer treatments shorter and more convenient for patients while maintaining excellent outcomes and low rates of toxicity.
In this study by Greco and colleagues, toxicity rates were low and similar between the SBRT and SDRT groups but trended toward higher genitourinary toxicity in the single-dose group. Additionally, biochemical RFS was slightly lower in this group, although the difference was not statistically significant.
This study shows the feasibility of SDRT, or “virtual prostatectomy,” which could make treatment more convenient for patients. However, we must balance the benefit of shorter treatment with the possibility of differences in control and toxicity compared with standard treatment. Although this is a promising new treatment, additional studies should be done in a larger population to further characterize the safety and efficacy over long-term follow up.
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