Stereotactic body radiotherapy (SBRT) resulted in fewer bowel-related side effects than a longer radiation regimen but failed to prove superior for disease control in men with intermediate-risk prostate cancer, according to a study published August 13 in JAMA. 

The finding is from a multinational team who evaluated SBRT against moderately hypofractionated intensity-modulated radiation therapy (MH-IMRT) in a phase III trial involving 698 patients over three years, noted lead author Rodney Ellis, MD, of the University of South Florida, and colleagues. 

“This study has immediate impact on patients and physicians considering a shorter course of radiotherapy for localized prostate cancer,” the group wrote. 

SBRT is inherently desirable from a patient convenience standpoint, given that treatment is delivered in five sessions over two weeks, compared with 20 to 28 daily sessions for MH-IMRT, the authors explained. Yet prior reports have raised concerns about adverse event rates with the faster approach, they added. 

To compare the techniques head-to-head, the researchers enrolled 698 men with intermediate-risk localized prostate cancer at 136 centers internationally, randomizing them 1:1 to SBRT (36.25 Gy in 5 fractions) or MH-IMRT (70 Gy in 28 fractions or 60 Gy in 20 fractions). They analyzed whether SBRT was superior to MH-IMRT in terms of patient-reported urinary irritative/obstructive and bowel quality of life and disease-free survival (DFS). 

According to the findings, at two years, there was no significant difference in the urinary-irritative domain (35.4% versus 33.7%, p = 0.68). Urinary incontinence at one and two years after treatment and sexual function at one year after treatment favored SBRT, and there were fewer grade 3 and 4 genitourinary adverse events in the SBRT versus MH-IMRT group (0.6% versus 2.5%, p = 0.04). 

Further, fewer patients in the SBRT group compared with the MH-IMRT group had minimal clinically important declines in bowel-related quality of life (34.9% versus 43.8%). At three years after treatment, SBRT was not superior to MH-IMRT in terms of DFS (88.6% for SBRT vs 92.1% for MH-IMRT), the researchers reported. 

“Stereotactic body radiotherapy using a modest dose prescription improved multiple quality-of-life domains but was not superior to MH-IMRT in terms of DFS,” the group wrote. 

Ultimately, because hundreds of thousands of men undergo prostate radiotherapy each year, how quickly patients can receive radiation treatment and the resultant toxicity of treatment is an issue that impacts not only patients and their caregiving teams but entire health care systems, the researchers noted. 

“Shared decision-making will be valuable when selecting not only the number of fractions but also the various dose/fraction schedules to optimize treatment outcomes that are most important to each individual patient,” the authors concluded. 

Read the full study here.