Whole Versus Partial Gland Boost During Prostate SBRT

This is a phase 2/3 randomized clinical trial evaluating two dose escalation strategies during prostate stereotactic body radiotherapy (SBRT). A total of 186 patients with prostate adenocarcinoma will be enrolled and randomized in a 1:1 ratio to one of two treatment arms.

In both arms, patients will receive 3625 cGy delivered to the planning target volume (PTV) over 5 fractions. In Arm A, patients will receive a boost to the prostate gland. In Arm B, patients will receive a boost to the dominant intra-prostatic lesion (DIL) identified on pre-treatment magnetic resonance imaging (MRI).

The primary objective is to evaluate chronic genitourinary (GU) and gastrointestinal (GI) toxicities grade 2 or higher from 6 months to 2 years post-treatment using the Common Terminology Criteria for Adverse Events (CTCAE). Secondary objectives include evaluation of acute and chronic GU and GI toxicities using CTCAE, Radiation Therapy Oncology Group (RTOG), and Expanded Prostate Cancer Index Composite (EPIC) domains, as well as biochemical progression-free survival at 5 years.

Participants will be followed for up to 5 years after completion of treatment.

Inclusion criteria

• Adults ≥19 years of age
• Patients with a diagnosis of prostate adenocarcinoma for which stereotactic body radiotherapy (SBRT) to the prostate ± proximal seminal vesicles is being offered
• Prostate gland volume <100 cc prior to initiation of androgen deprivation therapy (ADT), as reported at time of biopsy or by imaging (e.g., ultrasound, MRI, or CT)
• PI-RADS 4 or 5 lesion seen on pre-treatment MRI
• IPSS/AUA symptom score less than 16

Exclusion criteria

• Prior treatment for prostate cancer
• Prior solid cancer diagnosis within the last 5 years
• Any history of anal or rectal cancer
• Any history of invasive carcinoma of the bladder
• History of prior circumferential resection of the rectum (such as LAR or APR)