A Phase 1 Trial of Focal Salvage Stereotactic Body Radiation Therapy for Radiorecurrent Prostate Cancer

Area of Science:

• Radiation Oncology
• Urology
• Prostate Cancer Research

Background:

• Locally radiorecurrent prostate cancer after initial radiation therapy presents a treatment challenge.
• Salvage therapies are necessary for patients with isolated intraprostatic recurrence.
• Image-guided focal stereotactic body radiation therapy (SBRT) is an emerging option.

Purpose of the Study:

• To determine the maximum tolerated dose (MTD) of image-guided, focal, salvage SBRT for radiorecurrent prostate cancer.
• To assess biochemical control and imaging response following salvage focal SBRT.

Main Methods:

• Phase 1 trial with 3 dose levels (40, 42.5, 45 Gy in 5 fractions).
• Dose escalation followed a 3+3 design, with expansion at the MTD.
• Toxicities monitored using Common Terminology Criteria for Adverse Events v5.0.

Main Results:

• Eight patients received salvage focal SBRT with a median follow-up of 35 months.
• The MTD was determined to be 40 Gy in 5 fractions (DL1).
• The most common toxicity was grade ≥2 genitourinary (GU) toxicity; no grade ≥3 gastrointestinal (GI) toxicity observed.

Conclusions:

• The MTD for focal salvage SBRT in isolated intraprostatic radiorecurrence is 40 Gy in 5 fractions.
• This dose achieved 100% 24-month biochemical progression-free survival.
• Late grade ≥2 GU toxicity was the most frequent significant toxicity.