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.
Localized prostate cancer can be effectively treated with external beam radiotherapy (EBRT). Ultrahypofractionated radiotherapy has become an established treatment option because of its favorable radiobiological characteristics, shorter treatment duration, and improved patient convenience. Owing to the low alpha/beta ratio of prostate cancer, delivery of larger doses per fraction may provide radiobiological advantages while maintaining excellent tumor control. Proton beam therapy (PBT) offers unique dosimetric advantages over photon radiotherapy by reducing unnecessary radiation exposure to surrounding normal tissues through the Bragg peak effect. These characteristics may be particularly beneficial for ultrahypofractionated treatment, especially in patients with intermediate- or high-risk disease who require treatment of larger target volumes, including the seminal vesicles or pelvic lymph nodes. However, prospective data regarding the long-term efficacy, safety, patient-reported outcomes, and predictive factors associated with ultrahypofractionated proton beam therapy remain limited. This is a prospective, single-center observational cohort study conducted at the National Cancer Center, Republic of Korea. Approximately 50 adult patients with histologically confirmed localized prostate adenocarcinoma who are scheduled to undergo definitive ultrahypofractionated proton beam therapy will be prospectively enrolled after providing written informed consent. All participants will receive protocol-based ultrahypofractionated proton beam therapy consisting of 35-40 Gy(RBE) delivered in five fractions using image-guided proton therapy. Androgen deprivation therapy will be administered according to contemporary clinical guidelines and physician discretion when indicated. The primary objective of this study is to evaluate the long-term efficacy and safety of ultrahypofractionated proton beam therapy for localized prostate cancer. Secondary objectives include evaluation of biochemical recurrence-free survival, clinical progression-free survival, overall survival, acute and late treatment-related toxicity, and patient-reported quality of life. In addition, the study will prospectively investigate clinical characteristics, treatment planning parameters, dosimetric variables, and patient-reported outcome measures to identify factors associated with oncologic outcomes and treatment-related toxicity. Clinical information, treatment planning data, physician-reported adverse events, laboratory findings including prostate-specific antigen (PSA), imaging studies, and patient-reported outcome measures using the Expanded Prostate Cancer Index Composite for Clinical Practice (EPIC-CP) and the Visual Analog Scale (VAS) will be prospectively collected. Patients will be followed every three months during the first two years, every six months during years three and four, and annually thereafter according to institutional follow-up practice. The findings from this prospective cohort study are expected to provide high-quality evidence regarding the clinical effectiveness and safety of ultrahypofractionated proton beam therapy and to facilitate the development of individualized treatment strategies for patients with localized prostate cancer by identifying predictors of long-term oncologic outcomes and treatment-related toxicity.
Study Type
INTERVENTIONAL
Allocation
NA
Purpose
TREATMENT
Masking
NONE
Enrollment
50
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.
National Cancer Center, Korea
Goyang-si, Gyeonggi-do, South Korea
RECRUITINGBiochemical recurrence-free survival
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.
Time frame: Up to 5 years after completion of proton beam therapy
Patient-reported quality of life
Patient-reported quality of life will be assessed using the Expanded Prostate Cancer Index Composite for Clinical Practice (EPIC-CP). Scores range from 0 to 100, with higher scores indicating better urinary quality of life.
Time frame: baseline, postRT 1 month, 4 months, 7 months and 1 year
Clinical recurrence-free survival
Time from radiotherapy completion to first occurrence of any clinical recurrence (local, regional, or distant) or death. Recurrence will be confirmed by imaging studies and/or histopathological findings when available.
Time frame: Up to 5 years after completion of proton beam therapy
Overall survival
Time from completion of ultrahypofractionated proton beam therapy to death from any cause. Participants who are alive at the time of analysis will be censored at the date of the last follow-up.
Time frame: From completion of proton beam therapy to 5 years after treatment
Treatment-related genitourinary toxicity
Treatment-related genitourinary (GU) toxicity will be assessed according to the Common Terminology Criteria for Adverse Events (CTCAE) version 4.03. Acute toxicity is defined as adverse events occurring within 90 days after completion of proton beam therapy, and late toxicity as events occurring more than 90 days after treatment completion.
Time frame: Up to 5 years after completion of proton beam therapy
Treatment-related gastrointestinal toxicity
Treatment-related gastrointestinal (GI) toxicity will be assessed according to the Common Terminology Criteria for Adverse Events (CTCAE) version 4.03. Acute toxicity is defined as adverse events occurring within 90 days after completion of proton beam therapy, and late toxicity as events occurring more than 90 days after treatment completion.
Time frame: Up to 5 years after completion of proton beam therapy
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