The following is a summary of “Stereotactic Body Proton Therapy Versus Conventionally Fractionated Proton Therapy for Early Prostate Cancer: A Randomized, Controlled, Phase 3 Trial,” published in the July 2024 issue of Oncology by Toesca et al.

This study aimed to evaluate whether ultra-hypofractionated proton therapy delivered via stereotactic body proton therapy (SBPT) is comparable to conventionally fractionated proton therapy (CFPT) in treating early-stage prostate cancer.

Conducted as a multicenter, randomized, controlled, non-inferiority phase 3 trial, this study enrolled patients with histologically confirmed low-risk prostate adenocarcinoma (Gleason score group 1, PSA <10 ng/mL, clinical stage T1-2a N0 M0 per AJCC 7th ed.). Patients were randomly assigned initially in a 1:1 ratio and later in a 2:1 ratio to receive either SBPT (38 Gy in 5 fractions) or CFPT (79.2 Gy in 44 fractions). The primary endpoint was freedom from failure (FFF) at 2 years post-randomization. Non-inferiority for FFF was assessed using one-sided confidence intervals. Toxicities were compared at various time points using Fisher’s Exact test, while health-related quality-of-life (HRQoL) was analyzed using a mixed-effects linear model. The trial is registered with ClinicalTrials.gov (NCT01230866) and is closed to accrual.

Between December 10, 2010, and September 29, 2020, 144 patients were enrolled, with 135 randomly assigned (90 to SBPT, 45 to CFPT). Median follow-up was 5 years (IQR 3.9–5.2). The 2-year FFF rate was 100% in both groups, with a one-sided 5-year risk difference in FFF between groups of 2.63% (90% CI: -1.70%–6.96%), indicating non-inferiority of SBPT compared to CFPT. Rates of gastrointestinal (GI) and genitourinary (GU) G2 and G3 toxicities did not significantly differ, although the study was not powered to detect such differences. HRQoL metrics remained consistent across groups over the median follow-up period.

SBPT demonstrates non-inferiority to CFPT in achieving FFF outcomes for early-stage prostate cancer, with comparable rates of long-term GU and GI toxicities and minimal impact on patient-reported HRQoL over time. These findings support the feasibility and efficacy of SBPT as a potential treatment option in this patient population.

Source: sciencedirect.com/science/article/abs/pii/S0360301624006692