• Hiroshi Mayahara, Masao Murakami, Kazufumi Kagawa, Atsuya Kawaguchi, Yasue Oda, Daisuke Miyawaki, Ryohei Sasaki, Kazuro Sugimura, and Yoshio Hishikawa.
• Hyogo Ion Beam Medical Center, Hyogo, Japan. hmayahar@ncc.go.jp
• Int. J. Radiat. Oncol. Biol. Phys. 2007 Oct 1; 69 (2): 434-43.

PurposeTo investigate the incidence and influencing factors of acute genitourinary (GU) and gastrointestinal morbidities in patients with prostate cancer treated with proton therapy.Methods And MaterialsA total of 287 patients with histologically proven Stage cT1-T4N0M0 prostate cancer were treated with proton therapy between 2003 and 2004. Of these, 204 (71%) received neoadjuvant androgen suppression therapy. The patients were treated with 190-230-MeV protons using lateral-opposed techniques to a dose of 74 GyE. Dose-volume histogram analyses were performed. The incidence of acute morbidity was evaluated using the National Cancer Institute Common Toxicity Criteria, version 2.0. Clinical factors, including age, clinical target volume, initial prostate-specific antigen level, T stage, presence of diabetes mellitus, and the use of androgen suppression therapy, were investigated to determine whether those affected the incidence of acute GU morbidity.ResultsNone developed Grade 2 or higher acute gastrointestinal morbidity. In contrast, 111 (39%) and 4 (1%) patients experienced acute Grade 2 and Grade 3 GU morbidities, respectively. However, 87% of the patients were successfully relieved by the administration of a selective alpha-1 blocker. Multivariate analysis showed that a larger clinical target volume (p = 0.001) and the use of androgen suppression therapy (p = 0.017) were significant factors for the prediction of acute Grade 2-3 GU morbidity.ConclusionIn our experience with proton therapy, a low incidence of acute gastrointestinal morbidity was observed. In contrast, the incidence of acute GU morbidity was similar to that in other reports of photon radiotherapy. Additional follow-up is warranted to elucidate the long-term safety and efficacy of proton therapy for prostate cancer.

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