Prospective Study of Ultrahypofractionated Proton Beam Therapy for Localized Prostate Cancer

Condition(s) studied

Investigational drug(s) / intervention(s)

Ultrahypofractionated Proton Beam Therapy: Ultrahypofractionated proton beam therapy is delivered using pencil beam scanning (PBS) with image-guided proton therapy. Before treatment planning, all participants undergo placement of an absorbable rectal hydrogel spacer and two intraprostatic gold fiducial markers. Treatment planning is performed using CT simulation with MRI fusion after hydrogel stabilization. Daily cone-beam CT (CBCT) with fiducial marker matching is used for image guidance and patient positioning. A total dose of 36.25-40.0 Gy(RBE) is delivered in 5 fractions over approximately 1-2 weeks. Unlike conventional proton beam therapy using opposed right and left lateral beam arrangements, this protocol employs four oblique beam angles (right anterior oblique, right posterior oblique, left posterior oblique, and left anterior oblique) to optimize dose conformity while minimizing radiation exposure to adjacent normal tissues.

Study summary

The goal of this prospective observational cohort study is to evaluate the long-term efficacy and safety of ultrahypofractionated proton beam therapy in patients with localized prostate cancer and to identify clinical and treatment-related factors associated with oncologic outcomes and treatment-related toxicity.

The main questions it aims to answer are:

What are the long-term biochemical recurrence-free survival, clinical progression-free survival, overall survival, and acute and late treatment-related toxicity outcomes following ultrahypofractionated proton beam therapy? Which clinical characteristics, treatment planning parameters, and patient-reported outcomes are predictive of long-term oncologic outcomes and treatment-related toxicity?

Participants will:

Receive protocol-based ultrahypofractionated proton beam therapy (35-40 Gy\[RBE\] in 5 fractions).

Undergo routine clinical evaluation, laboratory testing including prostate-specific antigen (PSA), and imaging studies according to the institutional follow-up schedule.

Complete patient-reported outcome questionnaires (EPIC-CP and Visual Analog Scale \[VAS\]) before treatment and during follow-up.

Be followed prospectively to assess biochemical recurrence, clinical progression, survival outcomes, and acute and late treatment-related toxicities.

Eligibility

Primary outcome measure(s)

• Biochemical recurrence-free survival — Up to 5 years after completion of proton beam therapy
  Biochemical recurrence is defined according to the Phoenix definition (PSA nadir + 2 ng/mL). Biochemical recurrence-free survival is measured from completion of proton beam therapy to biochemical recurrence or last follow-up.

Trial sites (1)

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