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Updated: May 25, 2025

Proton Therapy Delivery and Its Clinical Application in Select Solid Tumor Malignancies
Published on: February 6, 2019
Efficacy and Safety of Newly Installed Spot Scanning Proton Beam Therapy for Prostate Cancer
Sachika Shiraishi1,2, Yukiyasu Horikawa3, Ryota Umeda3
1Department of Radiation Oncology, Shonan Kamakura General Hospital, Kamakura, Japan; s-nogi@tokyo-med.ac.jp.
Background/Aim:
This study aimed to analyse retrospectively the initial treatment outcomes and associated toxicities of a spot scanning proton beam therapy for prostate cancer at the Shonan-Kamakura General Hospital.
Patients And Methods:
A laterally opposing single-field uniform dose of spot-scanning proton beam was used. The doses were determined to be 60 Gy in 20 fractions for low-risk prostate cancer and 63 Gy in 21 fractions for intermediate- and high-risk prostate cancers. Genitourinary (GU) and gastrointestinal (GI) toxicities were also evaluated. Toxicity was assessed using the Common Terminology Criteria for Adverse Events (CTCAE) version 5.0.
Results:
A total of 135 patients were treated over two years, 51 of whom underwent hydrogel spacer insertion. During the limited observation period, no patient experienced a recurrence. Grade 2 GU toxicities were observed in 17 patients, whereas grade 1 or greater GI toxicities were observed in seven patients. None of the patients in whom a hydrogel spacer was inserted experienced grade 1 or higher GI toxicity.
Conclusion:
Proton beam therapy is safe for the treatment of prostate cancer. The insertion of a gold marker and hydrogel spacer led to a reduction in the rectal radiation dose and GI toxicity.

