A phase II trial of stereotactic body radiotherapy in 4 fractions for patients with localized prostate cancer

Abstract

Purpose/objective(s) To report results from our phase II study of stereotactic body radiotherapy (SBRT) delivering 36 Gy in 4 fractions for patients with localized prostate cancer. Materials/methods We enrolled 55 patients treated with SBRT delivering 36 Gy in 4 fractions between 2015 to 2018. All patients were categorized as low-risk (n = 4), intermediate-risk (n = 31) or high-risk (n = 20) according to National Comprehensive Cancer Network criteria. Median age was 73 years (range 54–86 years). Two-thirds of patients (n = 37) had received androgen-deprivation therapy for 3–46 months (median, 31 months). Median duration of follow-up was 36 months (range 1–54 months). We used Radiation Therapy Oncology Group and National Cancer Institute—Common Toxicity Criteria version 4 for toxicity assessments. Quality of life (QOL) outcomes were also evaluated using the Expanded Prostate Cancer Index Composite (EPIC). Results Protocol treatments were completed for all patients. Six patients experienced biochemical failures. Among these six patients, three patients experienced clinical failure. One patient showed bone metastasis before biochemical failure. One patient died of gastric cancer. The 3-year biochemical control rate was 89.8%. Acute grade 2 genitourinary (GU) and gastrointestinal (GI) toxicities were observed in 5 patients (9%) and 6 patients (11%), respectively. No grade 3 or higher acute toxicities were observed. Late grade 2 GU and GI toxicities were observed in 7 patients (13%) and 4 patients (7%), respectively. Late grade 3 GU and GI toxicities were observed in 1 patient (1.8%) each. EPIC scores decreased slightly during the acute phase and recovered within 3 months after treatment. Conclusion Our phase II study showed that SBRT delivering 36 Gy in 4 fractions was safe and effective with favorable QOL outcomes, although this regimen showed slightly more severe toxicities compared to current standards.

SABR-Dual: a phase II/III trial of two-fraction versus five-fraction stereotactic radiotherapy for localized low- and favorable intermediate-risk prostate cancer

“…While SABR in fewer than five fractions to the entire prostate has not yet been prospectively studied on this scale, there have been multiple phase I and II experiences published to date, supporting it’s essential safety. Kawakami et al published a phase II series of 55 patients who received SABR in four fractions (equivalent BED to 40 Gy in five fractions), demonstrating reasonable efficacy [ 26 ]. While they reported a slight increase in toxicity, they did not use peri-rectal spacers, and also included high risk patients, some of whom had T3 disease, and allowed for the potentially confounding factor of hormone therapy.…”

SABR-Dual: A phase II/III trial of two-fraction versus five-fraction stereotactic radiotherapy for localized low- and favorable intermediate-risk prostate cancer

“…While SABR in fewer than ve fractions to the entire prostate has not yet been prospectively studied on this scale, there have been multiple phase I and II experiences published to date, supporting it's essential safety. Kawakami et al published a phase II series of 55 patients who received SABR in four fractions (equivalent BED to 40 Gy in ve fractions), demonstrating reasonable e cacy (23). While they reported a slight increase in toxicity, they did not use peri-rectal spacers, and also included high risk patients, some of whom had T3 disease, and allowed for the potentially confounding factor of hormone therapy.…”