Two-fraction Proton Therapy With MRI Guidance for Prostate Cancer: A Phase II Trial

Genitourinary and gastrointestinal toxicity were evaluated based on the Common Terminology Criteria for Adverse Events (CTCAE, version 5.0) developed by the National Cancer Institute (NCI). Adverse effects within 3 months post-treatment are classified as acute toxicities, while those occurring after 3 months are considered late toxicities.

Gastrointestinal and genitourinary health-related quality of life (HQOL) are measured using the Expanded Prostate Cancer Index Composite (EPIC) questionnaire, which is a validated comprehensive instrument to measure the health-related quality of life among men with prostate cancer. EPIC consists of 5 primary domains, including urinary function, bowel habits, sexual function, hormonal functions, and overall satisfaction. Responses to each question form a Likert scale and are transformed to a 0-100 scale for each domain and subdomain, higher scores representing better HQOL.

Biochemical progression-free survival (bPFS) among participants will be assessed during clinical follow-up. bPFS is defined as the duration of time a localized prostate cancer patient remains free from biochemical recurrence after treatment. Biochemical recurrence is defined as a prostate-specific antigen (PSA) increase of 2 ng/mL above the nadir based on the Phoenix criteria (nadir + 2 ng/mL), confirmed by a second PSA value obtained three or more weeks later.

Distant metastasis (DM) refers to the spread of cancer cells from the prostate to distant sites outside the pelvic region. DF will be assessed during clinical follow-up using prostate-specific membrane antigen positron emission tomography (PSMA-PET), MRI, and/or other clinical imaging in cases of persistent PSA progression or emergence of symptoms. Distant metastasis free survival is defined as the duration of time from treatment completion date to the date of distant metastasis diagnosis by clinical imaging or death.

Local Failure (LF) refers to recurrent prostatic mass diagnosed by digital rectal examination, clinical imaging techniques like PSMA-PET and/or MRI, or histopathological confirmation of recurrence by biopsy. Local failure-free survival is defined as the duration of time from treatment completion date to date of local failure diagnosis or death.

Regional Failure (RF) refers to recurrent in the regional lymph nodes diagnosed by clinical imaging techniques like PSMA-PET and/or MRI. Regional failure-free survival is defined as the duration of time from treatment completion date to date of regional failure diagnosis or death.