Abstract
Background: Despite the increasing worldwide utilization of stereotactic body radiation therapy (SBRT) for prostate cancer, there are no known summative data regarding its safety and efficacy. To address this knowledge gap, we conducted a PRISMA-guided systematic review and meta-analysis of prospective prostate SBRT trials. Results: Fourteen trials with a total of 2,038 patients were included. Median follow-up was 37 months (range 6-55 months). Most patients had cT1-T2a, Gleason ≤7 disease with median pre-treatment PSAs of 5–10; 1,042 (51%) were low-risk, 744 (37%) were intermediate-risk, 158 (8%) were high-risk, and the remainder were unreported. Doses ranged from 33.5–50.0 Gy, most typically in 5 fractions, with nearly all studies delivering nondaily fractionation with some type of daily image guidance. Outcomes were converted into counts at the end of one year. The pooled rate of FFBF was 98% [95% confidence interval, 97–98%]. The pooled rate of late grade ≥3 gastrointestinal and genitourinary toxicities were 1% [0–5%] and 2% [1–3%], respectively. Methods: PubMed and Google Scholar were queried for prospective studies evaluating survival and/or toxicity outcomes in SBRT (≤5 fractions) for localized prostate cancer. Pooled rates of freedom from biochemical failure (FFBF) and late grades ≥3 gastrointestinal (GI) and genitourinary (GU) toxicities were assessed. Meta-analysis of proportions was logit transformed and pooled using generalized linear mixed models (both fixed and random effects) and subsequently back transformed to standard proportions. Conclusions: Despite the lack of long-term follow-up and heterogeneity of the available evidence, prostate SBRT affords appropriate biochemical control with few high-grade toxicities. These data have implications for ongoing worldwide utilization of prostate SBRT as well as ongoing prospective investigations.
Highlights
External beam radiation therapy (EBRT) for localized, non-metastatic prostate cancer (PC) has historically been delivered with conventionally fractionated doses of 1.8–2.0 Gy per fraction generally over the course of 40–44 treatments
PubMed and Google Scholar were queried for prospective studies evaluating survival and/or toxicity outcomes in stereotactic body radiation therapy (SBRT) (≤5 fractions) for localized prostate cancer
SBRT capitalizes on the low α/β ratio of PC and involves fractional doses even higher than hypofractionation
Summary
External beam radiation therapy (EBRT) for localized, non-metastatic prostate cancer (PC) has historically been delivered with conventionally fractionated doses of 1.8–2.0 Gy per fraction generally over the course of 40–44 treatments. Given the inconvenience of this regimen for patients and www.oncotarget.com concerns regarding the low α/β ratio of PC [1,2,3,4], prostate hypofractionation (most commonly 2.5–3.4 Gy per fraction) has come into better focus over the last decade, especially with the publication of randomized trials such as Radiation Therapy Oncology Group (RTOG) 0415, CHHIP, HYPRO, and PROFIT [5,6,7,8] In addition to these encouraging phase III data, together with the expansion of technologies such as image guidance platforms, stereotactic body radiation therapy (SBRT) has become a highly active area of ongoing research for localized prostate cancer.
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