Long-term data support SBRT for low-, intermediate-risk prostate cancer
medwireNews: Stereotactic body radiotherapy (SBRT) has a favorable long-term disease control and safety profile in the setting of low- or intermediate-risk prostate cancer, say US researchers who analyzed individual patient data from over 2000 prospectively treated men.
Since 2014 the National Comprehensive Cancer Network guidelines have included SBRT as an alternative to conventionally fractionated regimens, but have also cautioned that longer follow-up data are needed to assess the long-term efficacy and safety of the approach.
To address this need, Amar Kishan (University of California, Los Angeles, USA) and colleagues identified 2142 men who received SBRT for low-risk (55.3%) or intermediate-risk (32.3%) disease in the context of 10 single-center and two multicenter phase II clinical trials in 2000–2012. The median follow-up for the current study was 6.9 years.
As reported in JAMA Network Open, the 7-year cumulative incidence of biochemical recurrence was 4.5% for patients with low-risk disease and 10.2% for those at intermediate risk, while the 7-year distant metastases rates were 0.1% and 2.0%, respectively.
And when intermediate-risk patients were categorized into favorable and unfavorable subgroups, the cumulative incidences of biochemical recurrence at 7 years were 8.6% and 14.9%, respectively, and the corresponding rates of distant metastases were 1.7% and 3.0%.
Furthermore, 91.4% of men with low-risk prostate cancer were alive at the 7-year mark, as were 91.7% of those with intermediate-risk disease, with overall survival rates of 93.7% and 86.5% for patients with favorable and unfavorable intermediate-risk prostate cancer, respectively. None of the deaths were due to prostate cancer.
Kishan et al note that the incidence of acute (ie, within 90 days of SBRT receipt) and late severe toxic events was “low.” Over 7 years, acute genitourinary and gastrointestinal events of grade 3 or worse occurred in 0.60% and 0.09% of patients, respectively, while the cumulative incidences of late events of the same severity were a respective 2.4% and 0.4%.
“[M]uch of the aversion to SBRT is based on a preconceived risk of severe grade 3 or higher toxic events,” write the researchers, but these findings “suggest that this risk is minimal and commensurate with the risk after other, more widely accepted treatment modalities.”
And they conclude: “Although randomized trials comparing conventional or moderate hypofractionation regimens and SBRT are underway, the favorable outcomes described herein strongly suggest that SBRT be considered a standard option for treating low-risk and intermediate-risk [prostate cancer].”
medwireNews is an independent medical news service provided by Springer Healthcare. © 2019 Springer Healthcare part of the Springer Nature group